Off-chain v3 JSON-RPC API reference implementation

[xli]

• [ ] 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