feat: let admins notify all users about updated access codes

config/services.yaml

@@ -26,9 +26,8 @@ services:
         arguments:
             $logger: '@monolog.logger.audit'
 
-    # Booking notifications. The sender is also the To of every notification -- the actual
-    # recipients are Bcc'd -- so it has to be an address that may both send and receive.
-    App\Service\BookingNotifier:
+    # Every mail goes out from this address, one per recipient -- see App\Email\Mailer.
+    App\Email\Mailer:
         arguments:
             $sender: '%env(string:MAILER_FROM)%'