Introduce `attachment_url_to_postid` filter to let plugins manage the uploads location better.

Props mattwiebe. Fixes #31717.

git-svn-id: https://develop.svn.wordpress.org/trunk@31867 602fd350-edb4-49c9-b593-d223f7449a82

src/wp-includes/media.php

@@ -3409,6 +3409,16 @@ function attachment_url_to_postid( $url ) {
 	);
 	$post_id = $wpdb->get_var( $sql );
 
+	/**
+	 * Filter an attachment id found by URL.
+	 *
+	 * @since 4.2.0
+	 *
+	 * @param int|null $post_id  The post_id (if any) found by the function.
+	 * @param string   $url      The URL being looked up.
+	 */
+	$post_id = apply_filters( 'attachment_url_to_postid', $post_id, $url );
+
 	return (int) $post_id;
 }