Group classes can now be marked invite-only (us_offerings.access_mode).
Invite-only classes are hidden from the public catalog and reachable only
when the instructor lets someone in via one of three paths, managed from
My Lessons -> My Group Classes:
- Add students directly: enrols them now with a pending payment.
- Make available: grants registered students access to self-enrol through
the normal paid flow (multi-select, emailed a notice).
- Invite by email: tokenised registration invite tied to the class for a
non-account address; after they register the class becomes enrollable.
Reuses an existing pending invite instead of sending a second link.
New us_group_access table records grants; GET /offerings merges granted
invite-only classes for the caller; enrolment requires a grant
(403 invite_required) and flips it to enrolled on success.
composer test (487), composer lint, composer cs all pass.
Co-Authored-By: Claude Opus 4.8 <[email protected]>
