Seems oddly over-specific. Don't they send mails when it's approved/rejected? So is this basically a mail-filter connecting to slack? Just that it's using an API-key. How save is this API? How much can one screw up things or steal data with that key? And it seems rather expensive for such a one-trick task.
Maybe add some more signals to get a real value for the customer, like a real mail-filter, RSS and other newsfeeds (which is popular here) or some dozen more APIs.
Maybe add some more signals to get a real value for the customer, like a real mail-filter, RSS and other newsfeeds (which is popular here) or some dozen more APIs.