WooCommerce behavior in the Product Admin List View

[felipeelia]

Description of the Change

This PR adds proper support to the WooCommerce Product Admin List Screen.

Currently, to fetch products for the admin list screen, WooCommerce, through its WC_Admin_List_Table_Products class, runs a SQL query to get a list of IDs and uses that in the main WP_Query. As ElasticPress is only involved during the WP_Query, it does not take any part in the actual search of products but only in the fetch of products matching the list of IDs.

Users wanting to keep the current behavior can add the following snippet to their codebase:

add_filter( 'ep_woocommerce_integrate_admin_products_list', '__return_false' );

By default, ElasticPress will search in products titles, content, excerpts, SKUs and their product variation SKUs. Users wanting to change that list, can use a snippet like the following:

add_filter(
	'ep_woocommerce_admin_products_list_search_fields'
	function ( $search_fields ) {
		$search_fields[] = 'post_name'; // Add post_name
		unset( $search_fields['post_title'] ); // Remove post_title
		return $search_fields;
	}
);

Closes #781

Additional Context

Some reference links were listed in this comment.

Changelog Entry

Changed: WooCommerce products list in the Dashboard now properly leverages ElasticPress.

Credits

Props @felipeelia

[tott]

This looks good to me