fix: simplify reservation admin labels

backend/bookings/test_admin.py

@@ -160,3 +160,20 @@ class ReservationAdminTests(TestCase):
         check_in = CheckIn.objects.get(reservation=reservation)
         self.assertEqual(check_in.checked_in_by, self.admin_user)
         self.assertEqual(check_in.source, CheckIn.Source.MANUAL)
+
+    def test_reservation_string_is_concise_without_performance_details(self):
+        single_guest_reservation = Reservation.objects.create(
+            performance=self.performance,
+            name="Maria Rossi",
+            email="maria@example.com",
+            party_size=1,
+        )
+        group_reservation = Reservation.objects.create(
+            performance=self.performance,
+            name="Luca Bianchi",
+            email="luca@example.com",
+            party_size=3,
+        )
+
+        self.assertEqual(str(single_guest_reservation), "Maria Rossi")
+        self.assertEqual(str(group_reservation), "Luca Bianchi (3)")