Refund a captured payment

Refunds a payment that has been [captured](https://docs.adyen.com/api-explorer/#/CheckoutService/latest/post/payments/{paymentPspReference}/captures), and returns a unique reference for this request. You get the outcome of the request asynchronously, in a [**REFUND** webhook](https://docs.adyen.com/online-payments/refund#refund-webhook). You can refund either the full captured amount or a part of the captured amount. You can also perform multiple partial refunds, as long as their sum doesn't...