patch
https://api.preczn.com/v1/forms//contacts/
Form-scoped equivalent of PATCH /v1/merchants/:merchantId/contacts/:contactId. Resolves the merchant from the form record then delegates to ContactApiService. Returns 409 if the patch creates a canonical-identity collision. Returns 404 if the contact does not belong to the form's merchant.
Validation failure. Returns { errors: [{ path, message }] }.
Form, merchant, or contact not found.
Patch would create a canonical-identity collision.