Product demo model for Mantle with GraphQL fields

class-product.php

<?php
/**
 * Product class file.
 *
 * @package App\Models
 */

namespace App\Models;

use Mantle\Contracts\Database\Registrable;
use Mantle\Database\Model\Post;
use Mantle\Database\Model\Registration\Register_Post_Type;

/**
 * Product Model.
 */
class Product extends Post implements Registrable {
	use Register_Post_Type;

	/**
	 * Register the post type and other features.
	 */
	public static function boot() {
		\add_action( 'fm_post_product', [ __CLASS__, 'fieldmanager_fields' ] );
		\add_action( 'graphql_register_types', [ __CLASS__, 'register_graphql_fields' ] );
	}

	public static function fieldmanager_fields() {
		$fm = new \Fieldmanager_Group(
			[
				'name'           => 'attributes',
				'serialize_data' => false,
				'add_to_prefix'  => false,
				'children'       => [
					'price'     => new \Fieldmanager_TextField(
						[
							'label'       => __( 'Price', 'mantle-demo' ),
							'input_type'  => 'number',
							'description' => __( 'Unit price in cents', 'mantle-demo' ),
						]
					),
					'inventory' => new \Fieldmanager_TextField(
						[
							'label'      => __( 'Inventory', 'mantle-demo' ),
							'input_type' => 'number',
						]
					),
				],
			]
		);
		$fm->add_meta_box( __( 'Product Attributes', 'mantle-demo' ), [ 'product' ], 'side' );
	}

	public static function register_graphql_fields() {
		register_graphql_field( 'Product', 'price', [
			'type' => 'integer',
			'description' => __( 'The price of the product in cents', 'mantle-demo' ),
			'resolve' => function( $post ) {
				return get_post_meta( $post->ID, 'price', true );
			},
		] );

		register_graphql_field( 'Product', 'availability', [
			'type' => 'string',
			'description' => __( 'The availability of the product', 'mantle-demo' ),
			'resolve' => function( $post ) {
				if ( $post->post_status !== 'publish' ) {
					return strtoupper( $post->post_status );
				}
				return (int) get_post_meta( $post->ID, 'inventory', true ) > 0 ? 'AVAILABLE' : 'UNAVAILABLE';
			},
		] );
	}

	public static function get_registration_args(): array {
		return [
			'public'                => true,
			'rest_base'             => static::get_object_name(),
			'show_in_rest'          => true,
			'supports'              => [ 'title', 'editor', 'thumbnail', 'excerpt' ],
			'show_in_graphql'       => true,
			'graphql_single_name'   => 'product',
			'graphql_plural_name'   => 'products',
			'labels'                => [
				'name'                  => __( 'Products', 'mantle-demo' ),
				'singular_name'         => __( 'Product', 'mantle-demo' ),
				'all_items'             => __( 'All Products', 'mantle-demo' ),
				'archives'              => __( 'Product Archives', 'mantle-demo' ),
				'attributes'            => __( 'Product Attributes', 'mantle-demo' ),
				'insert_into_item'      => __( 'Insert into product', 'mantle-demo' ),
				'uploaded_to_this_item' => __( 'Uploaded to this product', 'mantle-demo' ),
				'featured_image'        => _x( 'Featured Image', 'Product', 'mantle-demo' ),
				'set_featured_image'    => _x( 'Set featured image', 'Product', 'mantle-demo' ),
				'remove_featured_image' => _x( 'Remove featured image', 'Product', 'mantle-demo' ),
				'use_featured_image'    => _x( 'Use as featured image', 'Product', 'mantle-demo' ),
				'filter_items_list'     => __( 'Filter products list', 'mantle-demo' ),
				'items_list_navigation' => __( 'Products list navigation', 'mantle-demo' ),
				'items_list'            => __( 'Products list', 'mantle-demo' ),
				'new_item'              => __( 'New Product', 'mantle-demo' ),
				'add_new'               => __( 'Add New', 'mantle-demo' ),
				'add_new_item'          => __( 'Add New Product', 'mantle-demo' ),
				'edit_item'             => __( 'Edit Product', 'mantle-demo' ),
				'view_item'             => __( 'View Product', 'mantle-demo' ),
				'view_items'            => __( 'View Products', 'mantle-demo' ),
				'search_items'          => __( 'Search products', 'mantle-demo' ),
				'not_found'             => __( 'No products found', 'mantle-demo' ),
				'not_found_in_trash'    => __( 'No products found in trash', 'mantle-demo' ),
				'parent_item_colon'     => __( 'Parent Product:', 'mantle-demo' ),
				'menu_name'             => __( 'Products', 'mantle-demo' ),
			],
		];
	}
}