Off-chain v3 JSON-RPC API reference implementation

- [ ] content detached jws encode, decode
- [ ] JsonRpc server
- [ ] Auth by content detached JWS
- [ ] Map JsonRpc error to http error
- [ ] JsonRpc client
- [ ] get_supported_methods method
- [ ] create_payment method
- [ ] get_account_identification method
- [ ] get_payment_signature method
- [ ] approve_payment method
- [ ] get_payment_status method
- [ ] cancel_payment method
- [ ] get_certificate_fingerprints method
- [ ] ping method
- [ ] sender_initiated_diem_id_exchange
- [ ] server process request idempotency

The issue names no files, tests, or entry points; begin by scoping the checklist into detached JWS handling, the JSON-RPC server and client, authentication, error mapping, and the listed payment methods. Done would require completing and validating every unchecked item, including request-idempotency and sender-initiated Diem ID exchange.

Vom Indexierungsmodell aus dem Issue-Text verfasst.