Cancels the hold of a two-step payment (auto_clearing = false) and releases the funds. The X-Action header must be gateway.payment.reverse. Reversal is possible only for a payment in status approved that is not cleared; for a cleared payment use gateway.payment.refund. The reversal creates a child reversal payment and is processed asynchronously; get the final status via gateway.payment.status (the payment gets status reversed) or gateway.request.status. A rejected reversal is returned with HTTP 200 as a failed reversal payment with status error; it is also listed in reverse_payments of the original payment. The full two-step flow (create, clearing or reverse, refund) is shown in Capture payment (clearing).