WordPress REST API. Add featured image to REST API response

featured-media-url.php

<?php
/**
 * Add this code without opening PHP tag into funcitons.php og your active theme or with any code snippets plugin
 */
add_action(
	'rest_api_init',
	function() {
		
		// Here you can specify post types slug where this field should be supported
		$supported_post_types = array(
			'post',
			'tours',
		);

		foreach ( $supported_post_types as $post_type ) {
			register_rest_field(
				$post_type,
				'featured_media_url',
				array(
					'get_callback' => function( $object ) {
						if ( ! has_post_thumbnail( $object['id'] ) ) {
							return '';
						} else {
							return get_the_post_thumbnail_url( $object['id'], 'thumbnail' );
						}
					},
					'schema' => array(
						'type' => 'string',
					),
				)
			);
		}

	}
);