Cancel a payment（DELETE: /v2/payments/{merchantPaymentId}）
CancelAPI is a cancellation of an order, RefundAPI is a refund for an accepted order.
Please use CancelAPI when the transaction status becomes unknown due to a timeout during payment request.
Note: Cancel API can only be used until 00:15 AM the day after the transaction occurs. Please use the Refund API to cancel/refund any subsequent orders.
Refund a payment（POST: /v2/refunds）
The RefundAPI is used to issue refunds for orders once accepted.