Custom SiteConfig for Sponsor Links and Logos

ConfigYAML

SiteConfig: 
  extensions: 
    - CustomSiteConfig

CustomSiteConfig.php

<?php 
class CustomSiteConfig extends DataExtension {

	private static $has_many = array( 
		'Sponsors' => 'Sponsor' 
	);

	public function updateCMSFields(FieldList $fields) {

		$config = GridFieldConfig_RecordEditor::create();

		$sponsorfield = GridField::create( 
			'Sponsors', 
			'Sponsors', 
			$this->owner->Sponsors(), 
			$config 
		);

		$fields->addFieldToTab('Root.Sponsors', $sponsorfield); 
	}

}

Sponsor.php

<?php 
class Sponsor extends DataObject {

	private static $db = array ( 
		'Link' => 'Varchar(255)', 
	);

	private static $has_one = array ( 
		'SiteConfig' => 'SiteConfig', 
		'Image' => 'Image', 
	);

	private static $summary_fields = array(
		"Image.CMSThumbnail",
		"Link"	
	);

	public function getCMSFields() {
		$fields = parent::getCMSFields();

		$fields->addFieldToTab('Root.Main', TextField::create('Link'));
		
		$sizeMB = 2; // 2 MB 
		$size = $sizeMB * 1024 * 1024; // 2 MB in bytes
		
		$uploadField = UploadField::create('Image', 'Sponsor Image');
		$uploadField->getValidator()->setAllowedMaxFileSize($size);

		$fields->removeByName('SiteConfig');

		$fields->addFieldToTab('Root.Main', $uploadField);

		return $fields; 
		
	} 
}

Template

<% loop $SiteConfig.Sponsors %> 
	<p><a href="$Link">$Image.SetWidth(150)</a></p>  
<% end_loop %>