Creates, signs, stores, and prepares on-chain minting for a Bill of Exchange document.
This API:

• validates request structure and required BOE fields,
• signs the BOE as a W3C credential,
• uploads raw + signed document to storage,
• initializes mint transaction signing flow,
• returns a WebAuthn signing URL (/sign?sessionId=...) to complete minting.

This API returns a redirect URL with sessionId to sign the transaction.
Use the GET endpoint /auth/session-response?sessionId=<sessionId> to retrieve the session result.
The response will include an object under the key wrappedDocument, which contains the content of the .tt file.

If using MCP, enter shipperDomain, holderAddress, and beneficiaryAddress explicitly.