feat: let admins notify all users about updated access codes

config/packages/messenger.yaml

@@ -21,7 +21,7 @@ framework:
             # Mail is deliberately NOT routed to async. Nothing starts a worker on the server --
             # deploy.php only stops them -- so a queued SendEmailMessage would be written to
             # messenger_messages and stay there, with no error anywhere and nobody notified.
-            # Sending happens in the request instead; BookingNotifier catches a transport
+            # Sending happens in the request instead; App\Email\Mailer catches a transport
             # failure so it can never fail the booking that triggered it. Route it back here
             # once a `messenger:consume async` worker actually runs.
             # Symfony\Component\Mailer\Messenger\SendEmailMessage: async