Cancel or refund a payment

Cancels a payment if it has not been captured yet, or refunds it if it has already been captured. This is useful when it is not certain if the payment has been captured or not (for example, when using auto-capture). Do not use this endpoint for payments that involve: * [Multiple partial captures](https://docs.adyen.com/online-payments/capture). * [Split data](https://docs.adyen.com/marketplaces-and-platforms/processing-payments#providing-split-information) either at time of payment or capt...