Quickstart

App start
  ├─ POST /login_check                    (only if no valid session)
  ├─ POST /user/do_action      get_profile
  ├─ POST /user/do_action      get_credit
  └─ POST /terminal/do_action  checkApiKey  (registers the device on first use)

Selling a voucher
  ├─ printVoucher            → print the returned data
  ├─ confirmVoucher          → after the printer reports success
  │
  ├─ (print failed?) reprintVoucher → print again → confirmReprintVoucher
  └─ (customer wants a copy later?) duplicateVoucher → print → confirmReprintVoucher

Other
  ├─ POST /vouchers          history
  ├─ POST /session/          close the current session and open a new one
  ├─ POST /token/refresh     whenever a call returns 401 "Expired JWT Token"
  └─ GET  /user/logout