Store the received encrypted data on the receiving Rafiki

[mkurapov]

Such that we can augment the incoming_payment.partial_payment_received webhook data with the payload to pass through to the receiving ASE

When the event is generated, it should store the decoded packet from the payload in the webhook event data - it could be encrypted lightly with a library like the standard node library and some secret perhaps derived from the environment.

// webhooks/event/model
{
  // ...webhook.event.model
  "encryptedData": string
}