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]>

docs/features/group-classes.md

@@ -48,6 +48,19 @@ cancelled enrolment does not block re-enrolling).
 Capacity is enforced at enrolment time by counting `active` rows for the offering;
 a class at capacity rejects further enrolments.
 
+Enrolment also closes after the class's **enrolment deadline** (the instructor's
+`enrollment_deadline`, defaulting to `term_start` — the first class day; see
+`offerings.md`). Past the deadline `POST /enrollments` rejects the enrolment with
+`403 enrollment_closed`, and the class list shows "Enrolment has closed." in place
+of the Enrol button.
+
+The deadline only bounds student **self**-enrolment. An instructor (or studio admin)
+can still enrol someone by hand from the class **details page** — the **Add students
+directly** control, available for every group class, deliberately bypasses the
+deadline (and capacity) so a **late enrolment** can be added after the class has
+closed. Past the deadline the details page labels these as late enrolments. See
+**Admin Interface** below.
+
 ## REST API
 | Method   | Endpoint                                     | Permission                       |
 |----------|----------------------------------------------|----------------------------------|
@@ -74,13 +87,15 @@ flips their grant from `invited` to `enrolled`.
 
 Access to an invite-only class is recorded in `{prefix}us_group_access` — a grant per
 person, separate from the enrolment itself. The instructor manages access from
-**My Lessons → My Group Classes**, which renders three controls under each invite-only
-class:
+**My Lessons → My Group Classes**. **Add students directly** is available on every
+class's details page (see **Admin Interface**); invite-only classes add two more
+controls beneath it:
 
 1. **Add students directly** — the selected registered students are enrolled immediately
    (`status = active`) with a **pending payment** at the class price (comp students are
    settled at once by `PaymentService`). No access grant is needed — this writes straight
-   to `us_group_enrollments` + `us_payments`.
+   to `us_group_enrollments` + `us_payments`. It bypasses the enrolment deadline and
+   capacity, so it doubles as the **late-enrolment** path after a class has closed.
 2. **Make available** — the selected registered students get an `invited` grant so the
    class appears in their own group-class list; they then self-enrol through the normal
    paid flow. Each is emailed a "you've been added" notice.
@@ -121,12 +136,14 @@ class becomes enrollable for them — they choose whether to enrol.
   against capacity, plus a **View details** link (**View & invite** for invite-only
   classes). Selecting a class (`?class_id=<id>`, scoped to the owning instructor) opens its
   **details page**: a class-details panel (when, instructor, enrolled/capacity, duration,
-  price, schedule note, description, status), the roster of enrolled students with enrolment
-  and payment status, and — for invite-only classes — an **Invite & enrol students** section
-  listing who has been invited but not yet enrolled alongside the add/make-available/
-  invite-by-email controls (nonce-checked `usc_action` POSTs, scoped to the owning
-  instructor). Managing who is in an invite-only class is therefore done entirely from this
-  page. The summary (`templates/admin/my-group-classes.php`) and the details page
+  price, schedule note, enrolment deadline, status), the roster of enrolled students with
+  enrolment and payment status, and an **Add students** section. Every class — public or
+  invite-only — carries the **Add students directly** control there, which enrols the
+  selected students immediately (a late enrolment past the deadline; the section says so
+  when the deadline has passed). Invite-only classes additionally get the
+  **make-available** and **invite-by-email** controls plus the list of who has been invited
+  but not yet enrolled. These are nonce-checked `usc_action` POSTs, scoped to the owning
+  instructor. The summary (`templates/admin/my-group-classes.php`) and the details page
   (`templates/admin/my-group-class-detail.php`) are separate templates.
 
 ## Implementation