Can’t retrieve custom post type taxonomy term to custom post type editor

To solve the problem of adding the editor_name custom field to the default WordPress REST API request for categories, we need to take a few steps to ensure that the custom field is correctly registered and included in the REST API responses.

1. Register the Custom Field in the REST API Response:
   You need to register the editor_name field to be included in the REST API responses for your custom taxonomy faq_category. You can do this using the register_rest_field() function.

Here’s how you can update your faqs-service.php file:

// Register the REST API routes for FAQ endpoints.
function faqs_api() {
    register_rest_route('wp/v2', '/faqs/categories', array(
        'methods' => 'GET',
        'callback' => 'get_faq_categories',
    ));

    register_rest_route('wp/v2', '/faqs/category/(?P<id>\d+)', array(
        'methods' => 'GET',
        'callback' => 'get_faqs_by_category_id',
    ));
}

// Register the custom field editor_name for the REST API response
function register_faq_category_fields() {
    register_rest_field('faq_category', 'editor_name', array(
        'get_callback' => 'get_faq_category_editor_name',
        'update_callback' => null,
        'schema' => null,
    ));
}

// Callback function to retrieve the editor_name field
function get_faq_category_editor_name($object, $field_name, $request) {
    return get_term_meta($object['id'], $field_name, true);
}

// Hook into the REST API initialization
add_action('rest_api_init', 'faqs_api');
add_action('rest_api_init', 'register_faq_category_fields');

2. Ensure the Field is Saved Properly:
   Make sure that the editor_name field is being saved correctly when you add or edit a category. You’ve already handled this in your save_faq_category_meta() function.

3. Modify the Custom REST Route (if needed):
   If you still want to use your custom REST routes, you should ensure that the editor_name field is included in the response. You’ve mostly handled this in the get_faq_categories() function by manually retrieving the editor_name meta field.

4. Testing the REST API:
   You can now test the REST API by accessing the endpoint. The default WordPress REST API query for faq_category should now include the editor_name field. The following request should retrieve the categories with the editor_name field included:
   http://localhost/wp-json/wp/v2/faq_category?context=view&per_page=100&orderby=name&order=asc&_fields=id,name,parent,editor_name&_locale=user

Troubleshooting:

Ensure caching is disabled: If you’re not seeing the expected results, ensure that no caching is interfering with your API responses.
Debugging: Add logging or debugging statements in your functions to track the flow and see if the fields are being fetched and added correctly.
With these changes, your editor_name field should be correctly added to the REST API responses for your custom taxonomy.