public function userConversations($user)
    {
        $userId = is_object($user) ? $user->getKey() : $user;

        return $this->join('mc_conversation_user', 'mc_conversation_user.conversation_id', '=', 'mc_conversations.id')
            ->where('mc_conversation_user.user_id', $userId)
            ->where('private', true)
            ->pluck('mc_conversations.id');
    }