Add rejectPartialIncomingPaymentAPI

[mkurapov]

Context

When the receiving ASE receives the incoming_payment.partial_payment_received webhook (built in RAF-1184), it perform its own payment checks and decide whether to accept the partial incoming payment or not. If the ASE chooses to reject the payment, they can call a new rejectPartialIncomingPayment mutation.

API

rejectPartialIncomingPayment

input RejectPartialIncomingPayment {
  incomingPaymentid: ID!
  partialIncomingPaymentId: ID!
  reason: String
}

This resolver will proceed to call a (new) method on the incoming payment service, in which it update the Redis object with key partial_payment_decision:{incomingPaymentId}:{partialIncomingPaymentId} and set it to the JSON.stringify({ approved: false, reason?: <string> }).