REST API: Accept POST requests in the block renderer endpoint.

Rendering a block is idempotent, so a GET is the most natural request method. However, the maximum length of URLs prevented blocks with large attributes from being rendered.

Props ryankienstra.
Fixes #49680.

Built from https://develop.svn.wordpress.org/trunk@47756


git-svn-id: http://core.svn.wordpress.org/trunk@47532 1a063a9b-81f0-0310-95a4-ce76da25c4cd

wp-includes/rest-api/endpoints/class-wp-rest-block-renderer-controller.php

@@ -52,7 +52,7 @@ class WP_REST_Block_Renderer_Controller extends WP_REST_Controller {
 						),
 					),
 					array(
-						'methods'             => WP_REST_Server::READABLE,
+						'methods'             => array( WP_REST_Server::READABLE, WP_REST_Server::CREATABLE ),
 						'callback'            => array( $this, 'get_item' ),
 						'permission_callback' => array( $this, 'get_item_permissions_check' ),
 						'args'                => array(