public function create($content, $object, array $users, $sender = null, $parent = null)
    {
        $message = new Message();
        $message->setContent($content);
        $message->setParent($parent);
        $message->setObject($object);
        $message->setSender($sender);
        $stringTo = '';

        foreach ($users as $user) {
            $stringTo .= $user->getUsername().';';
        }

        $message->setTo($stringTo);

        return $message;
    }