/v1 API.
Endpoints
Settlement & keys
The v2 endpoints: BLS key registration, co-signing, and settlement status
The endpoints added in v2, on top of the existing ads/trades API. All are
under the authenticated
The backend authorizes the signer as a trade party, verifies a confirmed
key is registered for that wallet on both trade chains, and rejects a
signature pair signed over different roots. Legible errors tell the client
exactly which wallet needs registration.