Implement protocol "invoice" flow

[bnonni]

Summary

There is a final part of the dcx protocol that has not been implemented yet: invoices. For information about the invoice schema, check out Invoice Schema for an understanding of how to structure these records.

Goal

Implement the invoice flow for both issuer and applicant sides of dcx. Issuers send invoice records to applicants following a application/response of type fulfillment. Applicants receive and pay invoices.

Possible payment methods

• DAPs Integrate DAP to pay for a credential #112
• Fiat rails (debit, credit, ach, wire)
• Out-of-band payments

Questions

• Can we integrate payment methods directly into the protocol somehow?
• Could payment methods be DWN protocols? If so, what would a 2-sided payment protocol look like.