REST API: Remove trailing slashes when preloading requests and add unit tests for it.

Props antonvlasenko.
Fixes #51636.
Built from https://develop.svn.wordpress.org/trunk@51648


git-svn-id: http://core.svn.wordpress.org/trunk@51254 1a063a9b-81f0-0310-95a4-ce76da25c4cd

wp-includes/rest-api.php

@@ -2818,6 +2818,11 @@ function rest_preload_api_request( $memo, $path ) {
 		}
 	}
 
+	$path = untrailingslashit( $path );
+	if ( empty( $path ) ) {
+		$path = '/';
+	}
+
 	$path_parts = parse_url( $path );
 	if ( false === $path_parts ) {
 		return $memo;

wp-includes/version.php

@@ -13,7 +13,7 @@
  *
  * @global string $wp_version
  */
-$wp_version = '5.9-alpha-51647';
+$wp_version = '5.9-alpha-51648';
 
 /**
  * Holds the WordPress DB revision, increments when changes are made to the WordPress DB schema.