handle adyen results more consistent

[arnelandwehr]

see discussion here: #12 (comment)

Both return types PurchaseResult and ModificationResult contains pspResults and errorStatusCodes.
But they are evaluated in different ways., preferable would be a more consistent flow in both cases.

[BLangendorf]

😼 Not sure if I understand the description, because ModificationResult is auto-generated code and the counterpart of PaymentResult (also auto-gen). Both contain neither pspResults nor errorStatusCodes but rather are PSP Results themselves …

@arnelandwehr maybe you meant another class than ModificationResult here?

[arnelandwehr]

ah right, got the wrong ones.

PaymentResult should be PurchaseResult
ModificationResult should be PaymentModificationResponse