Add group-class enrolment deadline with instructor late-enrolment override

Group classes gain an instructor-set enrolment deadline (new
us_offerings.enrollment_deadline column) that defaults to the first day of
the class (term_start). Past the deadline students can no longer self-enrol:
the enrolment endpoint rejects it (403 enrollment_closed) and the front-end
class list shows "Enrolment has closed." in place of the Enrol button.

Instructors keep a manual path: the "Add students directly" control on each
class's details page now renders for public classes too (not just
invite-only) and deliberately bypasses the deadline and capacity, so a
student can be added as a late enrolment after the class has closed. Past
the deadline the details page labels these as late enrolments.

Bumps USC_VERSION to 1.1.3 for the schema change.

Co-Authored-By: Claude Opus 4.8 <[email protected]>

src/GroupClass/GroupClassController.php

@@ -176,7 +176,7 @@ class GroupClassController {
 	 * invite-only classes — the list of people invited but not yet enrolled.
 	 *
 	 * @param list<Enrollment> $enrollments
-	 * @return array{id: int|null, title: string, when: string, capacity: int|null, enrolled: int, invite_only: bool, instructor: string, price: float, currency: string, duration: int|null, description: string|null, schedule_note: string|null, active: bool, roster: list<array{student: string, status: string, payment: string|null}>, invited: list<array{who: string, kind: string}>}
+	 * @return array{id: int|null, title: string, when: string, capacity: int|null, enrolled: int, invite_only: bool, instructor: string, price: float, currency: string, duration: int|null, description: string|null, schedule_note: string|null, deadline: string, enrollment_open: bool, active: bool, roster: list<array{student: string, status: string, payment: string|null}>, invited: list<array{who: string, kind: string}>}
 	 */
 	private function classDetail( Offering $offering, array $enrollments ): array {
 		$roster = [];
@@ -195,16 +195,20 @@ class GroupClassController {
 			];
 		}
 
+		$deadline = $offering->effectiveEnrollmentDeadline();
+
 		return $this->classSummary( $offering, $enrollments ) + [
-			'instructor'    => $this->instructorName( $offering ),
-			'price'         => $offering->price,
-			'currency'      => $offering->currency,
-			'duration'      => $offering->durationMinutes,
-			'description'   => $offering->description,
-			'schedule_note' => $offering->scheduleNote,
-			'active'        => $offering->isActive,
-			'roster'        => $roster,
-			'invited'       => $offering->isInviteOnly() ? $this->pendingInvites( (int) $offering->id ) : [],
+			'instructor'      => $this->instructorName( $offering ),
+			'price'           => $offering->price,
+			'currency'        => $offering->currency,
+			'duration'        => $offering->durationMinutes,
+			'description'     => $offering->description,
+			'schedule_note'   => $offering->scheduleNote,
+			'deadline'        => null !== $deadline ? (string) mysql2date( 'M j, Y', $deadline ) : '',
+			'enrollment_open' => $offering->isEnrollmentOpen( Val::string( current_time( 'Y-m-d' ) ) ),
+			'active'          => $offering->isActive,
+			'roster'          => $roster,
+			'invited'         => $offering->isInviteOnly() ? $this->pendingInvites( (int) $offering->id ) : [],
 		];
 	}
 
@@ -312,6 +316,10 @@ class GroupClassController {
 	 * Directly enrol registered students, each with a pending payment at the
 	 * class price (comp students are settled immediately by the payment service).
 	 *
+	 * This is the instructor's manual enrolment path and deliberately bypasses the
+	 * enrolment deadline and capacity, so a student can be added as a late
+	 * enrolment after the class has closed to self-enrolment.
+	 *
 	 * @param list<int> $studentIds
 	 */
 	private function addDirect( Offering $offering, array $studentIds ): string {