Accounting integration for iOS payment

[bedhub]

When receiving webhook callbacks from the apple payment system i want that they are tracked in the booking system so that our database state is consistent.

AC

• Booking items are created
  • when upgrading to a paid account
  • cancelling to free account
  • switching to higher/lower plan
  • renewing subscription
• Booking items should be created with a set totalInvoicedCount in case of upgrade or renewals
• Booking items include the price in € independent which foreign currency was used
• Monthly / yearly subscription are reflected in the Booking items
• The end date is tracked correctly (renewal, upgrade to higher plan).
• KPIs are tracked to count upgrades/downgrades
• When the payment method iOS is configure there should be additional restrictions
  • Account termination is not allowed
  • Adding and reactivating users is prevented.
  • Granting credit is not allowed

*Tasks

• [x] Create booking items
• [x] Implement restrictions
• [x] Switch subscription when we receive notification from Apple
• [x] Check if InvoiceBatchJob will work if payment method was changed from AppStore before the run
• [x] Add state diagram for account state + notifications + user actions
• [ ] Bug: It is possible to switch plans without changing App Store Subscription