Supplier destination change

This reference application runs an initiator and a supplier-master receiver as two local FastAPI services. It demonstrates why approving a destination change is a different effect from later releasing a payment.

uv run pytest -q examples/supplier_destination/test_example.py

The example includes:

• confidential extracted bank details;
• separate initiator and receiver authentication boundaries;
• dual authority;
• request, tenant, audience, state, and replay binding at the receiver;
• authoritative verification of the receiver's state; and
• a later payment bound to the verified supplier-destination version.

Its application/v0 transport envelope belongs only to the example. It is not a proposed public protocol.

Start with domain.py, then follow the initiator_service.py and receiver_service.py boundaries. The full failure matrix lives in test_example.py.