where('conversation_id', $message->conversation_id) ->where('user_id', $user->id) ->whereNull('left_at') ->exists(); } public function update(User $user, Message $message): bool { return $message->sender_id === $user->id && $message->deleted_at === null; } public function delete(User $user, Message $message): bool { return $message->sender_id === $user->id || $user->isAdmin(); } }