/**
	 * Retrieves all of the registered additional fields for a given object-type.
	 *
	 * Overrides wp core `get_additional_fields()` to allow excluding fields.
	 *
	 * @since 1.0.0-beta.27
	 *
	 * @param string $object_type The object type.
	 * @return array Registered additional fields (if any), empty array if none or if the object type could
	 *               not be inferred.
	 */
	protected function get_additional_fields( $object_type = null ) {

		// We require the `$this->schema['properties']` to be set in order to exclude additional fields already covered by our schema definition.
		if ( ! isset( $this->schema['properties'] ) ) {
			return parent::get_additional_fields( $object_type );
		}

		$additional_fields = parent::get_additional_fields( $object_type );
		if ( ! empty( $additional_fields ) ) {
			/**
			 * Filters the disallowed additional fields.
			 *
			 * The dynamic portion of the hook name, `$object_type`, refers the object type this controller is responsible for managing.
			 *
			 * @since 1.0.0-beta.27
			 *
			 * @param string[] $disallowed_additional_fields Additional rest field names to skip (added via `register_rest_field()`).
			 */
			$disallowed_fields = apply_filters( "llms_rest_{$object_type}_disallowed_additional_fields", $this->disallowed_additional_fields );

			/**
			 * Exclude:
			 * - disallowed fields defined in the instance's property `disallowed_additional_fields`.
			 * - additional fields already covered in the schema.
			 *
			 * This is meant to run only once, because otherwise we have no way
			 * to determine whether the property comes from the original schema
			 * definition, or has been added via `register_rest_field()`.
			 */
			$additional_fields = array_diff_key(
				$additional_fields,
				array_flip( array_keys( $this->schema['properties'] ) ),
				array_flip( $disallowed_fields )
			);

		}

		return $additional_fields;

	}

	/**
	 * Exclude disallowed meta fields.
	 *