public function between($userOne, $userTwo)
    {
        $conversation1 = $this->conversation->userConversations($userOne)->toArray();
        $conversation2 = $this->conversation->userConversations($userTwo)->toArray();

        $common_conversations = $this->getConversationsInCommon($conversation1, $conversation2);

        if (!$common_conversations) {
            return;
        }

        return $this->conversation->findOrFail($common_conversations[0]);
    }