Accepts the composite or a bare pspReference (all a cancel needs). An empty
or whitespace-only reference is refused with invalid_request, so capture,
cancel and refund send nothing for it: the empty pspPaymentId
completePayment reports while it holds no reference is not one.
Accepts the composite or a bare pspReference (all a cancel needs). An empty or whitespace-only reference is refused with invalid_request, so capture, cancel and refund send nothing for it: the empty
pspPaymentIdcompletePayment reports while it holds no reference is not one.