Users & claim

claim (recommended)

Create deal without link. Unlinked parties get claim_url. User signs up and is seated as buyer/seller.

Option A — link

POST /api/v1/users/link

{
  "external_user_id": "mkt_buyer_99",
  "trustlayer_user_id": "8d956c75-…"
}

Use field name trustlayer_user_id (not user_id).