REST API Custom Fields
This plugin enhances WordPress REST API v2 responses about metadata.
The metadata enhancement is available only for this wordpress core object types: post, comment, user, term
Upload “rest-api-custom-fields” folder to the “/wp-content/plugins/” directory.
Activate the plugin through the “Plugins” menu in WordPress.
New item “REST API Custom Fields” appears in the admin menu (under the Settings menu). There you can select which metadata you want to contain in the REST API response.