Search a post by its slug

You need to update the `functions.php` file in WordPress and include the following code to allow metadata to be updated via the API:

function expose_metadata() {
      register_rest_field(
           'post',
           'post_meta_fields',
           array(
                'get_callback' => 'callback_read_post_meta',
                'update_callback' => 'callback_update_post_meta',
                'schema' => null,
           )
      );
}

function callback_read_post_meta( $object ) {
      $post_id = $object['id'];
      return get_post_meta( $post_id );
}

function callback_update_post_meta( $meta_value, $object, $field_name ) {
      $post_id = $object->ID;

      if (!is_array( $meta_value ) ) {
           return new WP_Error( 'rest_invalid_param', __( 'El valor debe ser un array de campos de metadatos.' ), array( 'status' => 400 ) );
      }

      foreach ( $meta_value as $meta_key => $meta_value ) {
           update_post_meta( $post_id, sanitize_key( $meta_key ), sanitize_text_field( $meta_value ) );
      }
      return true;
}

add_action( 'rest_api_init', 'expose_metadata' );

This error indicates that the user doesn't have the necessary permissions to edit posts in the specific context where the action is being attempted.

To resolve this issue, it's necessary to ensure that the user has the appropriate permissions. An alternative that might work would be to modify the 'context' field in your task and select the option 'Extract the entry for viewing'.