Declined card throws exception in OrdersCaptureAsync()

[ianw1223]

When testing the declined card scenario by using CCREJECT-REFUSED in the payer name field, OrdersCaptureAsync() throws an exception.

Surely a refused card is an expected scenario, not an exception. OrdersCaptureAsync should return an informative result that we can handle as a normal part of our workflow, rather than having details buried within the exception.