Add invite-only group classes

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]>

src/RestRegistrar.php

@@ -9,6 +9,7 @@ use Unsupervised\Schedular\Booking\BookingEndpoint;
 use Unsupervised\Schedular\Booking\BookingRepository;
 use Unsupervised\Schedular\Booking\CancellationPolicy;
 use Unsupervised\Schedular\GroupClass\EnrollmentEndpoint;
+use Unsupervised\Schedular\GroupClass\GroupAccessRepository;
 use Unsupervised\Schedular\GroupClass\EnrollmentRepository;
 use Unsupervised\Schedular\Offering\OfferingEndpoint;
 use Unsupervised\Schedular\Offering\OfferingRepository;
@@ -35,13 +36,13 @@ class RestRegistrar {
 	private EnrollmentEndpoint $enrollmentEndpoint;
 	private PaymentEndpoint $paymentEndpoint;
 
-	public function __construct( AvailabilityRepository $availability, BookingRepository $bookings, OfferingRepository $offerings, QuestionRepository $questions, PolicyRepository $policies, PolicyVersionRepository $policyVersions, PolicyService $policyService, RegistrationGate $gate, EnrollmentRepository $enrollments, PaymentService $paymentService ) {
+	public function __construct( AvailabilityRepository $availability, BookingRepository $bookings, OfferingRepository $offerings, QuestionRepository $questions, PolicyRepository $policies, PolicyVersionRepository $policyVersions, PolicyService $policyService, RegistrationGate $gate, EnrollmentRepository $enrollments, GroupAccessRepository $groupAccess, PaymentService $paymentService ) {
 		$this->availabilityEndpoint = new AvailabilityEndpoint( $availability, $offerings );
 		$this->bookingEndpoint      = new BookingEndpoint( $availability, $bookings, $offerings, $gate, $paymentService, new CancellationPolicy( new StudioSettings() ) );
-		$this->offeringEndpoint     = new OfferingEndpoint( $offerings );
+		$this->offeringEndpoint     = new OfferingEndpoint( $offerings, $groupAccess );
 		$this->questionEndpoint     = new QuestionEndpoint( $questions, $offerings );
 		$this->policyEndpoint       = new PolicyEndpoint( $policies, $policyVersions, $policyService );
-		$this->enrollmentEndpoint   = new EnrollmentEndpoint( $enrollments, $offerings, $gate, $paymentService );
+		$this->enrollmentEndpoint   = new EnrollmentEndpoint( $enrollments, $offerings, $gate, $paymentService, $groupAccess );
 		$this->paymentEndpoint      = new PaymentEndpoint( $paymentService );
 	}