REST API: Disable `DELETE` requests for users in multisite.

In wp-admin, users are removed from individual sites rather than deleted. A user can only be deleted from the network admin.

Until support for a `PUT` request that removes a user's site and content associations is available, `DELETE` requests are disabled to avoid possible issues with lost content.

Props jnylen0, rachelbaker.
Fixes #38962.

Built from https://develop.svn.wordpress.org/trunk@39438


git-svn-id: http://core.svn.wordpress.org/trunk@39378 1a063a9b-81f0-0310-95a4-ce76da25c4cd

wp-includes/rest-api/endpoints/class-wp-rest-users-controller.php

@@ -701,6 +701,11 @@ class WP_REST_Users_Controller extends WP_REST_Controller {
 	 * @return WP_REST_Response|WP_Error Response object on success, or WP_Error object on failure.
 	 */
 	public function delete_item( $request ) {
+		// We don't support delete requests in multisite.
+		if ( is_multisite() ) {
+			return new WP_Error( 'rest_cannot_delete', __( 'The user cannot be deleted.' ), array( 'status' => 501 ) );
+		}
+
 		$id       = (int) $request['id'];
 		$reassign = false === $request['reassign'] ? null : absint( $request['reassign'] );
 		$force    = isset( $request['force'] ) ? (bool) $request['force'] : false;

wp-includes/version.php

@@ -4,7 +4,7 @@
  *
  * @global string $wp_version
  */
-$wp_version = '4.8-alpha-39436';
+$wp_version = '4.8-alpha-39438';
 
 /**
  * Holds the WordPress DB revision, increments when changes are made to the WordPress DB schema.