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]>

tests/Unit/GroupClass/EnrollmentEndpointTest.php

@@ -32,6 +32,7 @@ class EnrollmentEndpointTest extends TestCase
         Functions\when('wp_unslash')->returnArg();
         Functions\when('sanitize_text_field')->returnArg();
         Functions\when('get_current_user_id')->justReturn(5);
+        Functions\when('current_time')->justReturn('2026-07-24');
 
         $this->enrollments = Mockery::mock(EnrollmentRepository::class);
         $this->offerings   = Mockery::mock(OfferingRepository::class);
@@ -108,6 +109,36 @@ class EnrollmentEndpointTest extends TestCase
         );
     }
 
+    public function testRejectsEnrollmentAfterExplicitDeadline(): void
+    {
+        // current_time is stubbed to 2026-07-24, past the 2026-07-10 deadline.
+        $offering = new Offering(instructorId: 3, kind: Offering::KIND_GROUP_CLASS, title: 'Choir', termStart: '2026-07-01', enrollmentDeadline: '2026-07-10', id: 8);
+        $this->offerings->shouldReceive('findById')->with(8)->andReturn($offering);
+        $this->enrollments->shouldReceive('hasActiveEnrollment')->with(8, 5)->andReturn(false);
+        $this->enrollments->shouldReceive('insert')->never();
+
+        $result = $this->endpoint->enroll(new \WP_REST_Request(['offering_id' => 8]));
+
+        self::assertInstanceOf(\WP_Error::class, $result);
+        self::assertSame('enrollment_closed', $result->get_error_code());
+        self::assertSame(403, $result->error_data['enrollment_closed']['status']);
+    }
+
+    public function testRejectsEnrollmentAfterDefaultDeadlineOfFirstClassDay(): void
+    {
+        // No explicit deadline, so it defaults to term_start (the first class day),
+        // which is in the past relative to the stubbed 2026-07-24 "today".
+        $offering = new Offering(instructorId: 3, kind: Offering::KIND_GROUP_CLASS, title: 'Choir', termStart: '2026-07-20', id: 8);
+        $this->offerings->shouldReceive('findById')->with(8)->andReturn($offering);
+        $this->enrollments->shouldReceive('hasActiveEnrollment')->with(8, 5)->andReturn(false);
+        $this->enrollments->shouldReceive('insert')->never();
+
+        $result = $this->endpoint->enroll(new \WP_REST_Request(['offering_id' => 8]));
+
+        self::assertInstanceOf(\WP_Error::class, $result);
+        self::assertSame('enrollment_closed', $result->get_error_code());
+    }
+
     public function testInviteOnlyClassRejectsStudentWithoutGrant(): void
     {
         $this->offerings->shouldReceive('findById')->with(8)->andReturn($this->inviteOnlyOffering());