This is set of helper classes to create and manage custom post types for WordPress. It gets added to a theme's logic folder, or libs or includes folders, and included in functions.php. Then the primary tracker class is initiated once, and used to create new CTPs.

custom_post_types.php

<?php

/***********************************************************************/
/***************************  TRACKER CLASS  ***************************/
/***********************************************************************/

if ( ! class_exists( 'Custom_Post_Types_Manager' ) ) {

	class Custom_Post_Types_Manager {

		public $ctp_slugs;
		public $prefix;

		function __construct($init_data) {

			$this->prefix = $init_data['prefix'];
			$this->ctp_slugs = array();

		}

		public function setup_ctp($ctp_options) {

			$ctp_options['prefix'] = $this->prefix;

			$ctp = new Custom_Post_Type($ctp_options);

			array_push( $this->ctp_slugs, $ctp->full_slug() );

		}

		public function get_slugs() {

			return $this->ctp_slugs;

		}

	}

}



/***********************************************************************/
/***********************  INDIVIDUAL CTP CLASS  ************************/
/***********************************************************************/

if ( ! class_exists( 'Custom_Post_Type' ) ) {

	class Custom_Post_Type {

		public $prefix;
		public $slug;
		public $custom_strings;
		public $supports;
		public $menu_icon;
		public $icon;
		public $metaboxes;
		public $metadata;

		function __construct($init_data) {

			$this->prefix         = array_key_exists('prefix', $init_data) ? $init_data['prefix'] : null;
			$this->slug           = array_key_exists('slug', $init_data) ? $init_data['slug'] : null;
			$this->custom_strings = array_key_exists('custom_strings', $init_data) ? $init_data['custom_strings'] : null;
			$this->taxonomy_slug  = array_key_exists('taxonomy_slug', $init_data) ? $init_data['taxonomy_slug'] : null;
			$this->supports       = array_key_exists('supports', $init_data) ? $init_data['supports'] : array( 'title', 'editor' );
			$this->menu_icon       = array_key_exists('menu_icon', $init_data) ? $init_data['menu_icon'] : null;
			$this->icon           = array_key_exists('icon', $init_data) ? $init_data['icon'] : null;
			$this->metaboxes      = array_key_exists('metaboxes', $init_data) ? $init_data['metaboxes'] : null;
			$this->metadata      = array_key_exists('metadata', $init_data) ? $init_data['metadata'] : null;
			$this->display_page = array_key_exists('display_page', $init_data) ? $init_data['display_page'] : null;
			$this->hierarchical = array_key_exists('hierarchical', $init_data) ? $init_data['hierarchical'] : false;
			$this->min_role = array_key_exists('min_role', $init_data) ? $init_data['min_role'] : null;

			$this->capabilities = $this->build_capabilities( $this->min_role );

			add_action( 'init', array( &$this, 'create_ctp' ) );
			add_action( 'admin_head', array( &$this, 'create_ctp_icons' ) );
			add_action( 'save_post', array( &$this, 'save_ctp_custom_metadata' ), 10, 3 );
			add_action( 'rest_api_init', array( &$this, 'expose_metadata_via_restapi' ) );

		}

		private function build_capabilities() {

			// WORDPRESS DOESN'T GIVE THE ABILITY DIRECTLY TO SPECIFIC MINIMUM USER ROLES TO SEE
			// AND INTERACT WITH A CTP. BUT YOU CAN MAP CAPABILITIIES. KINDA HARD TO EXPLAIN, BUT
			// BASICALLY, YOU CAN SPECIFY A min_role IN THE CTP CREATION OPTIONS NOW, AND THIS
			// FUNCTION WILL GRAB A CAPABILITY OF THE ROLE THAT YOU HAVE SPECIFIED. IT THEN MAPS
			// THE CAPABILITIES THAT HANDLE INTERACTING WITH THE CTP, TO THE CAPABILITY DECIDED HERE

			$capability_to_match = null;

			switch ( $this->min_role ) {

				case 'administrator' :

					$capability_to_match = 'update_core';

					break;

				case 'editor' :

					$capability_to_match = 'edit_pages';

					break;

				case 'author' :

					$capability_to_match = 'publish_posts';

					break;

				case 'contributor' :

					$capability_to_match = 'edit_posts';

					break;

			}

			if ( $capability_to_match ) {

				return array(
					'publish_posts' => $capability_to_match,
					'edit_posts' => $capability_to_match,
					'edit_others_posts' => $capability_to_match,
					'delete_posts' => $capability_to_match,
					'delete_others_posts' => $capability_to_match,
					'read_private_posts' => $capability_to_match,
					'edit_post' => $capability_to_match,
					'delete_post' => $capability_to_match,
					'read_post' => $capability_to_match
				);

			} else {

				return null;

			}

		}

		public function full_slug() {

			return ($this->prefix)?strtolower($this->prefix.'_'.$this->slug):$this->slug;

		}

		public function create_ctp() {

			$post_type_slug = $this->full_slug();
			$post_label = ucfirst( $this->slug );


			// SPECIFY THE ARGUMENTS FOR THE CTP, THEN REGISTER IT

			$args = array(
				'labels' => array(
					'name' => $post_label.'s',
					'singular_name' => $post_label,
					'all_items' => $post_label.' '.__( 'List' ),
					'add_new' => 'Add New'.' '.$post_label,
					'add_new_item' => 'Add New'.' '.$post_label,
					'edit_item' => 'Edit'.' '.$post_label,
					'new_item' => 'New'.' '.$post_label,
					'view_item' => 'View'.' '.$post_label,
					'search_items' => 'Search',
					'not_found' =>  'Not found',
					'not_found_in_trash' => 'Trash is empty'
				),
				'hierarchical' => $this->hierarchical,
				'public' => true,
				'show_in_rest' => true,
				'has_archive' => true,
				'supports' => $this->supports,
				'menu_icon' => $this->menu_icon,
				'register_meta_box_cb' => array( $this, 'create_ctp_custom_metaboxes' ),
			);

			/**
			 * Rewrite strings for the custom ones
			 */
			array_walk($args["labels"],function (&$v, $k) {
				if(array_key_exists($k, $this->custom_strings))
					$v = $this->custom_strings[$k];
			});


			if ( $this->taxonomy_slug ) {
				$taxonomy_slug = $post_type_slug.'_'.$this->taxonomy_slug;
				$taxonomy_label = ucwords( str_replace( '_', ' ', $this->taxonomy_slug ) );

				// SPECIFY THE ARGUMENTS FOR THE CTP'S TAXONOMY, THEN REGISTER IT

				$tax_args = array(
					'labels' => array(
						'name' => $taxonomy_label,
						'add_new_item' => 'Add New '.$taxonomy_label
					),
					'public' => true,
					'show_ui' => true,
					'show_tagcloud' => true,
					'hierarchical' => true,
					'show_in_nav_menus' => true,
					'show_admin_column' => true
				);

				register_taxonomy($taxonomy_slug, $post_type_slug, $tax_args);
				$args['taxonomies'] = array( $taxonomy_slug );
			} /*else {
				$taxonomy_slug = $post_type_slug.'_type';
				$taxonomy_label = $post_label.' Type';
			}*/


			// OPTIONAL ARGUMENTS

			if ( $this->display_page ) {

				$args['rewrite'] = array( 'slug' => $this->display_page,'with_front' => false );

			}

			if ( $this->capabilities ) {

				$args['capabilities'] = $this->capabilities;

			}

			register_post_type($post_type_slug, $args);

		}

		public function create_ctp_custom_metaboxes( $post ) {

			$post_type_slug = get_post_type($post);

			if ( $this->metaboxes != null ) {

				foreach ($this->metaboxes as $metabox) {

					$metabox_id = $post_type_slug.'_metabox_'.$metabox['slug'];
					$metabox_label = $metabox['label'];
					$metabox_callback = array( $this, 'create_ctp_custom_metadata' );
					$metabox_screen = $post_type_slug;
					$metabox_content = $metabox['position'];
					$metabox_priority = 'default';
					$metabox_callback_args = array( $metabox['metadata'], $post_type_slug );

					add_meta_box($metabox_id, $metabox_label, $metabox_callback, $metabox_screen, $metabox_content, $metabox_priority, $metabox_callback_args );

				}

			}

		}

		public function create_ctp_custom_metadata($post, $data) {

			global $admin_colors;
			$metadata = $data['args'][0];
			$post_type_slug = $data['args'][1];

			$html = '';

			foreach ( $metadata as $metadatum ) {

				$html .= '<div class="metadata-wrap">';


				$metadatum_type = array_key_exists('type', $metadatum) ? $metadatum['type'] : 'text';
				$metadatum_label = array_key_exists('label', $metadatum) ? $metadatum['label'] : '';
				$metadatum_desc = array_key_exists('desc', $metadatum) ? $metadatum['desc'] : '';
				$metadatum_slug = array_key_exists('slug', $metadatum) ? $metadatum['slug'] : '';
				$metadatum_default = array_key_exists('default', $metadatum) ? $metadatum['default'] : '';
				$metadatum_options = array_key_exists('options', $metadatum) ? $metadatum['options'] : '';

				$metadatum_id = $post_type_slug . '_metadata_' . $metadatum_slug;
				$metadatum_value = get_post_meta($post->ID, $metadatum_id, true);
				$metadatum_value = $metadatum_value ? $metadatum_value : $metadatum_default;

				register_meta( $post_type_slug, $metadatum_id, array(
					'single' => true,
					'show_in_rest' => true
				));

				switch ( $metadatum_type ) {

					case 'hidden' :

						$html .= '<input type="hidden" name="' . $metadatum_id .'" id="' . $metadatum_id .'" value="' . $metadatum_value . '" class="widefat" />';

						break;

					case 'select' :

						$html .= '<p class="post-attributes-label-wrapper"><label class="post-attributes-label" for="' . $metadatum_id . '">' . $metadatum_label .'</label></p>';

						$html .= '<div class="metadata-desc">' . $metadatum_desc .'</div>';

						$html .= '<select name="' . $metadatum_id .'" id="' . $metadatum_id .'" class="widefat">';

						foreach ( $metadatum_options as $metadatum_option_label => $metadatum_option_value  ) {

							$html .= '<option' . ( $metadatum_option_value == $metadatum_value ? ' selected="selected"' : '' ) . ' value="' . $metadatum_option_value . '">' . $metadatum_option_label . '</option>';

						}

						$html .= '</select>';

						break;

					case 'textarea' :

						$html .= '<p class="post-attributes-label-wrapper"><label class="post-attributes-label" for="' . $metadatum_id . '">' . $metadatum_label .'</label></p>';

						$html .= '<div class="metadata-desc">' . $metadatum_desc .'</div>';

						$html .= '<textarea name="' . $metadatum_id .'" id="' . $metadatum_id .'" class="widefat">' . $metadatum_value . '</textarea>';

						break;

					case 'textarea_googlemappolygon' :

						$html .= '<p class="post-attributes-label-wrapper"><label class="post-attributes-label" for="' . $metadatum_id . '">' . $metadatum_label .'</label></p>';

						$html .= '<div class="metadata-desc">' . $metadatum_desc .'</div>';

						$html .= '<div id="map-wrap" style="max-height:400px;height:80vw;margin-bottom:10px"></div>';

						$html .= '<p class="post-attributes-label-wrapper"><label class="post-attributes-label" for="' . $metadatum_id . '">Encoded Polygon (Creates the Above Preview)</label></p>';

						$html .= '<textarea style="min-height:200px;" name="' . $metadatum_id . '" id="' . $metadatum_id . '" class="widefat">' . $metadatum_value . '</textarea>';

						$html .= '

						<script>

							(function(window, Mapstractor) {

								window.setTimeout(function(){

									// Grab Input Elements that Control the Map
									var encodedCoordinatesElement = document.getElementById(\'' . $metadatum_id . '\');
									var colorElement = document.getElementById(\'' . str_replace('shape', 'color', $metadatum_id) . '\');
									var polygon = null;

									// Setup Map
									var map = new Mapstractor({
										mapWrapID: \'map-wrap\',
										mapOptions: {
											center: {
												lat: 40,
												lng: -95
											},
											zoom: 4,
											minZoom: 3,
											maxZoom: 9,
											scrollwheel: true,
											draggable: true,
											mapTypeControl:false,
											streetViewControl:false,
											zoomControl:false,
											mapTypeId: google.maps.MapTypeId.ROADMAP,
										}
									});

									// Add Polygon to Map
									if ( encodedCoordinatesElement.value ) {
										polygon = map.addPolygon({
											encodedCoordinates: encodedCoordinatesElement.value,
											color: colorElement.value
										});
										map.gMap.panTo(polygon.getCenter());
									}

									// Add Event Listener to Preview Changes
									encodedCoordinatesElement.addEventListener(\'change\', function() {
										if ( encodedCoordinatesElement.value ) {
											if ( polygon == null ) {
												polygon = map.addPolygon({
													encodedCoordinates: encodedCoordinatesElement.value,
													color: colorElement.value
												});
												map.gMap.panTo(polygon.getCenter());
											} else {
												polygon.setOptions({paths: google.maps.geometry.encoding.decodePath(encodedCoordinatesElement.value)});
												map.gMap.panTo(polygon.getCenter());
											}
										} else {
											polygon.setMap(null);
											polygon = null;
										}
									}, false);
									colorElement.addEventListener(\'change\', function() {
										polygon.setOptions({fillColor: colorElement.value});
									}, false);

								}, 100);

							}(window, window.Mapstractor || (window.Mapstractor == {})));

						</script>

						';

						break;

					case 'text_googleaddress' :

						$metadatum_value_latlng = get_post_meta($post->ID, $metadatum_id.'_latlng', true);

						$html .= '<p class="post-attributes-label-wrapper"><label class="post-attributes-label" for="' . $metadatum_id . '">' . $metadatum_label .'</label></p>';

						$html .= '<div class="metadata-desc">' . $metadatum_desc .'</div>';

						$html .= '<textarea name="' . $metadatum_id .'" id="' . $metadatum_id .'" class="widefat">' . $metadatum_value . '</textarea>';

						$html .= '<input type="hidden" name="' . $metadatum_id .'_latlng" id="' . $metadatum_id .'_latlng" value="' . $metadatum_value_latlng . '" class="widefat">';

						$html .= '

						<script>

							(function(window, google) {

								var addressBoxElement = document.getElementById(\'' . $metadatum_id . '\');
								var latlngBoxElement = document.getElementById(\'' . $metadatum_id . '_latlng\');
								var addressBox = new google.maps.places.Autocomplete(addressBoxElement, {types: [\'address\'] });
								addressBox.addListener(\'place_changed\', function() {
									var selectedPlace = addressBox.getPlace();
									addressBoxElement.value = selectedPlace.formatted_address.replace(\', USA\',\'\');
									latlngBoxElement.value = selectedPlace.geometry.location.lat() + \',\' + selectedPlace.geometry.location.lng();
								});

							}(window, google));

						</script>

						';

						break;

					case 'toggle' :

						$html .= '
							<style>
								toggle::after {
									display:block;
									clear:both;
									content:"";
								}
								toggle input {
									position:absolute;
									left:-99999999px;
								}
								toggle svg {
									height:20px;
									width:20px;
									display:block;
								}
								toggle label div {
									display:block;
									float:left;
									padding:6px 12px;
									border:solid 1px rgb(160,160,160);
									fill:gray;
									position: relative;
								}
								toggle label:first-child div {
									border-radius:5px 0 0 5px;
									left: 1px;
								}
								toggle label:last-child div {
									border-radius:0 5px 5px 0;
									right: 1px;
								}
								toggle input:checked ~ div {
									color:white;
									fill:white;
									background-color: ' . $admin_colors . ';
									border-color: ' . $admin_colors . ';
									z-index:1;
								}
							</style>';

						$html .= '<p class="post-attributes-label-wrapper"><label class="post-attributes-label">' . $metadatum_label .'</div></p>';

						$html .= '<div class="metadata-desc">' . $metadatum_desc .'</div>';

						$html .= '<toggle>';

						foreach ( $metadatum_options as $metadatum_option ) {

							$html .= '<label><input type="radio" name="' . $metadatum_id .'"' . ( $metadatum_option['value'] == $metadatum_value ? ' checked="checked"' : '' ) . ' value="' . $metadatum_option['value'] . '"><div>' . $metadatum_option['label'] . '</div></label>';

						}

						$html .= '</toggle>';

						break;

					default :

						$html .= '<p class="post-attributes-label-wrapper"><label class="post-attributes-label" for="' . $metadatum_id . '">' . $metadatum_label .'</label></p>';

						$html .= '<div class="metadata-desc">' . $metadatum_desc .'</div>';

						$html .= '<input type="' . $metadatum_type . '" name="' . $metadatum_id .'" id="' . $metadatum_id .'" value="' . $metadatum_value . '" class="widefat" />';

						break;

				}

				$html .= '</div>';

			}

			echo $html . '<input type="hidden" name="custommeta_noncename" id="custommeta_noncename" value="' . wp_create_nonce( basename(__FILE__) ) . '" />';

		}

		public function expose_metadata_via_restapi() {

			if ( $this->metaboxes != null ) {

				foreach ($this->metaboxes as $metabox) {

					foreach ( $metabox['metadata'] as $metadatum ) {

						register_rest_field($this->full_slug(), $this->full_slug(). '_metadata_' . $metadatum['slug'],
							array(
								'get_callback'    => array( $this, 'slug_get_post_meta_cb' ),
								'update_callback' => array( $this, 'slug_update_post_meta_cb' ),
								'schema'          => null,
							)
						);

					}

				}

			}

		}

		public function slug_get_post_meta_cb( $object, $field_name, $request ) {

			return get_post_meta( $object['id'], $field_name );

		}

		public function slug_update_post_meta_cb( $value, $object, $field_name ) {

			return update_post_meta( $object['id'], $field_name, $value );

		}

		public function save_ctp_custom_metadata( $post_id, $post, $update ) {

			if (empty($_POST["custommeta_noncename"])) {
				return;
			}
			if ( ! wp_verify_nonce( $_POST['custommeta_noncename'], basename(__FILE__) )) {
				return;
			}
			if ( ! current_user_can( 'edit_post', $post->ID )) {
				return;
			}
			if ( $post->post_type == 'revision' ) {
				return;
			}

			$post_type_slug = get_post_type($post);
			$metadata_id = '';
			$metadata_object = array();

			if ( $this->metaboxes != null ) {

				foreach ( $this->metaboxes as $metabox ) {

					foreach ( $metabox['metadata'] as $metadatum ) {
						$metadata_id = $post_type_slug . '_metadata_' . $metadatum['slug'];
						$metadata_object[$metadata_id] = $_POST[$metadata_id];
						if ( $metadatum['type'] == 'text_googleaddress' ) {
							$metadata_id = $post_type_slug . '_metadata_' . $metadatum['slug'].'_latlng';
							$metadata_object[$metadata_id] = $_POST[$metadata_id];
						}

					}

				}

			}

			// Add values of $metadata_saving as custom fields
			foreach ($metadata_object as $key => $value) {
				$value = implode(',', (array)$value);
				if (get_post_meta($post->ID, $key, FALSE)) {
					update_post_meta($post->ID, $key, $value);
				} else {
					add_post_meta($post->ID, $key, $value);
				} if (!$value) {
					delete_post_meta($post->ID, $key);
				}
			}

		}

		public function create_ctp_icons(){

			if ( $this->icon !== null ) {

				echo '<style>#adminmenu #menu-posts-' . $this->full_slug() . ' div.wp-menu-image:before {content: "' . $this->icon . '";}</style>';

			}

		}

	}

}

Added: custom strings , menu_icon
Updated: optional taxonomy (if not set)