Read or configure an existing course public registration form. The link is stable and is never generated or rotated. Locked courses and courses without a registration link are rejected. Custom fields use the same names as training registration forms. This endpoint neither enrolls students nor sends invitations.

Partial update: omitted settings and resource flags remain unchanged. If a field is set to null → its value is reset (enrollment only: disables training enrollment). fields replaces the full field selection: omitted configurable fields are hidden and optional, while firstName/lastName remain visible and mandatory. mandatory: true requires displayed: true. Enrollment changes require an active training in the same school; all-false flags enroll without attaching resources. Untouched disabled resource groups keep their stored choices; editing a disabled group does not reactivate omitted choices.