post https://api.flexpay.io/v1/gateways/successfulpayment
Notify FlexPay of a successful payment from a customer in engaged recovery and to stop the engaged recovery outreach. Even though the Payment Method object is required to be sent as part of the "Successful Payment" request , creditCardNumber, gatewayPaymentMethodId and PaymentMethodId are not required since FlexPay will not reach out to the gateway