Current

Voucher support

Add vouchers (CLI) (done)
Cancel voucher (CLI)
Pay with voucher
- UI: Choose voucher or Venmo
  - Submission (done)
  - Display error state
  - Show current balance (time permitting)
- Service
  - Handling states:
    - Ok (done)
    - Not found (done)
    - Insufficient funds (done)
    - Disabled