Send a written testimonial with consent (Authorization: Bearer <link code>). One per link; a repeat returns the first.
Body: { kind: 'written', first_name, signer_name, agreed: true, wording_sha256, written_text (1-2000 chars) }. 409 wording_changed; 410 revoked / expired / binding_lost.
POST
https://api.channelautomation.com/api/field-sales/public/testimonial-links/submit