R1:28941b31059b

Update PhortuneMerchant to Modular Transactions

Summary: Modernize PhortuneMerchant for Modular Transactions. Also changed the language of "Members" to "Managers", which I think fits better given the power/capability.

Test Plan:
- Create a new Merchant
- Test not filling in a name, see error
- Test removing myself, see error
- Edit an existing Merchant
- Add new managers
- Test removing myself, see error
- Replace Picture
- Update various fields, contact info, email, footer
- Verify transactions are now…