post
https://api.preczn.com/v1/merchants//contacts
Creates a new contact on the merchant. The canonical key is (firstName.trim(), lastName.trim(), email.trim().toLowerCase()). If a contact with the same canonical key already exists on this merchant, the existing record is returned with HTTP 200 (no new row is created). A genuinely new contact returns HTTP 201.
401Unauthorized (test-mode mismatch).
403Forbidden (platform mismatch).
404Merchant not found.
