Implement missing tests for 3.x

[vernondegoede]

• [ ] Implement tests
  • [ ] Using global order discount
  • [x] Using order line discounts
  • [ ] Using 1 TaxRate per order line
  • [ ] Using 2 TaxRates per order line (it should throw an exception).
  • [x] MoneyFormatter (using both EUR, JPY and USD)
  • [ ] PaymentStateUpdater
  • [ ] Make sure order confirmation is only sent for authorized & paid orders