Refactor adyen hpp spec
Refactor adyen hpp spec

Pulled all the api stubbing out into a seperate shared context, this
should make it easier to stub api operations in the future.

StemboltHQ/solidus-adyen,freerunningtech/solidus-adyen,StemboltHQ/solidus-adyen,StemboltHQ/solidus-adyen,freerunningtech/solidus-adyen,freerunningtech/solidus-adyen,freerunningtech/solidus-adyen,StemboltHQ/solidus-adyen