Sandbox endpoint to simulate an incoming wire transfer

Broker API

Adds POST /v1/testing/incoming_wires (Simulate an Incoming Wire Transfer) to the Broker API reference. The operation is sandbox-only and returns 403 in production.

• New CreateSimulatedIncomingWireRequest and SimulatedIncomingWire schemas, with request and response examples.
• currency is optional and defaults to USD; wire_instructions must contain an FFC string matching FFC [0-9A-Za-z]{4}[-\s]?[0-9A-Za-z]{9}.
• Documents 400, 403, 404, 422, and default error responses.
• The description for POST /v1/accounts/{account_id}/transfers now points to this operation for funding an account with an incoming wire in sandbox.

Affected Endpoints

• POST /v1/testing/incoming_wires
• POST /v1/accounts/{account_id}/transfers