Start or resume a test-only MSA e-signature (business)

Creates (or resumes) the test-only SignWell signing attempt for the caller's own MSA document and returns the signature resource, plus a short-lived embedded signing URL when one is available for the calling signer. Records no MSA acceptance and has no legal effect. Without retry it returns the existing attempt even when that attempt has failed, been declined, expired or been canceled, so automatic resume calls can never start a second signing attempt; retry=true starts one new attempt after such an outcome, and a completed signature is never replaced. A signature started by another member of the business answers 409 without a URL; a document the caller cannot address answers 404.