Enforce telegram_message_id uniqueness through database index instead of in Rails, to prevent race condition when Telegram webhook sends the same payload multiple times and we check if the todo already exists, it doesn't, and then just when we are about to INSERT it into the database, another thread receives the same payload also checks the database, doesn't see it yet, and then BOTH records are INSERT'ed leading to duplicate todos despite checking for uniqnuess #wip