feat: enable entering additional remarks in offer confirmation

src/Controller/Admin/AccommodationBooking/SendAccessLinkController.php

@@ -35,6 +35,14 @@ class SendAccessLinkController extends AbstractController
                 throw $this->createAccessDeniedException('Invalid CSRF token.');
             }
 
+            // Older bookings can still be missing their contact data. Sending would be
+            // silently skipped further down, so say so instead of reporting success.
+            if (null === $booking->getEmail() || '' === trim($booking->getEmail())) {
+                $this->addFlash('error', 'Für diese Buchung ist keine E-Mail-Adresse hinterlegt. Bitte ergänze sie, um den Zugangslink zu senden.');
+
+                return new HxRedirectResponse($this->generateUrl('app_admin_accommodationbooking_edit', ['id' => $booking->getId()]));
+            }
+
             $this->bookingService->sendCustomerConfirmationEmail($booking);
 
             $this->addFlash('success', 'Der Zugangslink wurde dem Kunden per E-Mail zugestellt.');