post https://api.sandbox.rainforestpay.com/v1/payins//void_or_refund
Void or refund a payin by the payin ID.
If the payin status is Processing, then the full payin amount can be voided. A payin cannot be partially voided. If the payin status is Succeeded, then the payin can be fully or partially refunded. See the payin refundable_amount and non_refundable_reason_code for details on if the payin is eligible for a void or refund.