public static function setMappings(
        array $messages,
        /*# bool */ $manual = true
    ) {
        $class = get_called_class();

        if ($manual) {
            // set default
            static::$messages = $messages;

            // status changed
            self::setStatus();
        } else {
            // set cache
            self::$mappings[$class] = array_replace(
                $class::getMappings(),
                $messages
            );
        }
    }