Skip payment step for unpriced bookings, confirm them immediately, show students their lessons

Booking a slot with no priced offering created the lesson but no payment,
yet the front end still called POST /payments/intent, which 400ed with
"Could not start payment for this registration" — the student saw an error
while the backend held a claimed slot and a lesson stuck at pending.

- POST /bookings and POST /enrollments now return a `payment` summary
  ({id, method, status}) or null when nothing is owed; the JS only runs
  the payment step when a payment exists.
- Bookings with nothing owed are confirmed at creation — there is no
  payment step that would ever confirm them later.
- The booking page now shows the student's upcoming lessons (GET /bookings,
  now scoped to upcoming non-cancelled lessons with slot start/end times)
  with a pending-payment/confirmed status badge.

Fixes #53

Co-Authored-By: Claude Fable 5 <[email protected]>

assets/js/booking.js

@@ -5,9 +5,10 @@
     const app = document.getElementById('us-booking-app');
     if (!app) return;
 
-    const slotList = document.getElementById('us-slot-list');
-    const confirm  = document.getElementById('us-booking-confirmation');
-    const errorBox = document.getElementById('us-booking-error');
+    const slotList  = document.getElementById('us-slot-list');
+    const myLessons = document.getElementById('us-my-lessons');
+    const confirm   = document.getElementById('us-booking-confirmation');
+    const errorBox  = document.getElementById('us-booking-error');
     const { restUrl, nonce } = usScheduler;
 
     function apiFetch(path, options = {}) {
@@ -274,11 +275,51 @@
                 accepted_policy_version_ids: accepted,
             }),
         })
-            .then((res) => window.usPayment.collect('lesson', (res.ids || [])[0], slotList))
-            .then((result) => showConfirmation(window.usPayment.message(result)))
+            // A booking with nothing owed has no payment, so there is no payment
+            // step to run — the booking is already confirmed server-side.
+            .then((res) => (res.payment
+                ? window.usPayment.collect('lesson', (res.ids || [])[0], slotList)
+                : null))
+            .then((result) => {
+                loadMyLessons();
+                showConfirmation(window.usPayment.message(result));
+            })
             .catch((err) => showError(err.message));
     }
 
+    function lessonStatusLabel(status) {
+        if (status === 'pending') return 'Pending payment';
+        if (status === 'confirmed') return 'Confirmed';
+        return status.charAt(0).toUpperCase() + status.slice(1);
+    }
+
+    function renderMyLessons(lessons) {
+        const upcoming = lessons.filter((l) => l.start_dt);
+        if (!upcoming.length) {
+            myLessons.innerHTML = '';
+            return;
+        }
+
+        myLessons.innerHTML = `
+            <div class="us-my-lessons">
+                <h3>Your upcoming lessons</h3>
+                ${upcoming.map((l) => `
+                    <div class="us-my-lesson">
+                        <span>${escHtml(dayLabel(dayKey(l.start_dt)))} · ${escHtml(timeOf(l.start_dt))}–${escHtml(timeOf(l.end_dt))}</span>
+                        <span class="us-lesson-status us-lesson-status-${escHtml(String(l.status))}">${escHtml(lessonStatusLabel(String(l.status)))}</span>
+                    </div>
+                `).join('')}
+            </div>`;
+    }
+
+    function loadMyLessons() {
+        if (!myLessons) return;
+        // The lesson list is a bonus panel: never let it break slot browsing.
+        apiFetch('bookings')
+            .then(renderMyLessons)
+            .catch(() => { myLessons.innerHTML = ''; });
+    }
+
     function showConfirmation(message) {
         confirm.textContent = message;
         slotList.style.display = 'none';
@@ -289,6 +330,7 @@
         clearError();
         slotList.style.display = 'block';
         confirm.style.display = 'none';
+        loadMyLessons();
         apiFetch('availability')
             .then((slots) => {
                 allSlots = slots;