Booking confirmation email + customer self-service cancel/reschedule (#18)

Sends a confirmation email (best-effort, fire-and-forget SMTP via mailer.py)
on booking creation, with a manage-booking link embedding the ticket-2 signed
token. Adds /manage/<token>, a stateless cancel/reschedule page that reuses
the existing slot-picker against booking_api's create/cancel/reschedule API,
distinguishing an invalid/expired link from an already-cancelled one. Sender
address uses the client's own domain when configured, falling back to a
mivanchenko.de address otherwise.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

backoffice/app/tests/test_booking_api.py

@@ -72,6 +72,36 @@ def test_create_booking_auto_confirm_true_yields_confirmed(client):
     assert "token" in body
 
 
+def test_create_booking_via_public_endpoint_sends_confirmation_email(client, monkeypatch):
+    """#18's acceptance criterion: completing a booking via ticket 3's public
+    page (this same POST /api/booking endpoint) triggers the confirmation
+    email, with the manage-booking token embedded in it."""
+    sent = []
+    monkeypatch.setattr(
+        "booking_mail.mailer.send_email",
+        lambda to, subject, html, from_addr=None: sent.append(
+            {"to": to, "subject": subject, "html": html, "from_addr": from_addr}))
+    resource, service = _setup_resource_and_service(
+        auto_confirm=True, min_notice_minutes=0, max_advance_days=365)
+    day = _next_monday(date.today())
+    slots = client.get("/api/booking/slots", query_string={
+        "client_id": CLIENT_A, "resource_id": resource["resource_id"],
+        "service_id": service["service_id"],
+        "date_from": day.isoformat(), "date_to": day.isoformat()}).get_json()["slots"]
+
+    resp = client.post("/api/booking", json={
+        "client_id": CLIENT_A, "resource_id": resource["resource_id"],
+        "service_id": service["service_id"], "start_time": slots[0],
+        "customer_name": "Kim", "customer_contact": "kim@example.com"})
+    assert resp.status_code == 201
+    token = resp.get_json()["token"]
+
+    assert len(sent) == 1
+    assert sent[0]["to"] == "kim@example.com"
+    assert f"/manage/{token}" in sent[0]["html"]
+    assert "Haircut" in sent[0]["html"]
+
+
 def test_create_booking_auto_confirm_false_yields_pending(client):
     resource, service = _setup_resource_and_service(
         auto_confirm=False, min_notice_minutes=0, max_advance_days=365)
@@ -251,12 +281,12 @@ def test_reschedule_to_same_slot_is_a_noop_success(client):
 
 def test_manage_token_is_scoped_to_its_own_client():
     resource, service = _setup_resource_and_service(client_id=CLIENT_A)
-    from booking_api import _mint_manage_token, _verify_manage_token
+    from booking_api import _mint_manage_token, verify_manage_token
     booking = bdb.create_booking(
         CLIENT_A, resource["resource_id"], "Ivy", "i@example.com", "Haircut",
         datetime.now(timezone.utc) + timedelta(days=1),
         datetime.now(timezone.utc) + timedelta(days=1, hours=1))
     token = _mint_manage_token(CLIENT_A, booking["booking_id"])
-    assert _verify_manage_token(token) == (CLIENT_A, booking["booking_id"])
+    assert verify_manage_token(token) == (CLIENT_A, booking["booking_id"])
     tampered = token[:-1] + ("A" if token[-1] != "A" else "B")
-    assert _verify_manage_token(tampered) is None
+    assert verify_manage_token(tampered) is None