Epic: Integrate with Splitwise to keep up with expenses

[stephenyeargin]

If the prospect if building out an entire accounting system within the application is unappealing, the Splitwise API may be beneficial. It allows for the creation of expenses assigned to a user (an email address) and can process the payments through a handful of processors.

• We OAuth a bot (not sure if we should auth individuals, but a bot seems plausible)
• Bot creates a group that aligns 1-to-1 with the SeatShare group (tracks Splitwise group ID)
• Bot adds expenses for individual tickets when transfer request is processed (track expense ID with request)
• Bot can cancel a given expense when a ticket request is cancelled
• Users can log into Splitwise to make payments or edit terms
• Platform pulls in current balances for group