Some use cases (e.g., paying for fuel at a service station) involve
pre-authorization of payment. One way to do this is through a Payment Handler
(see the Payment Handler API).
Currently that specification includes a CanMakePayment that a
Payment Handler could make use of, to return authorization status.
Payment Request success. Demo complete. No payment has been taken.
The Payment Request API is unsupported or was cancelled or failed, so here we can proceed with our legacy web form (not implemented for this demo).