feat: let admins notify all users about updated access codes

templates/admin/access_codes.html.twig

@@ -20,10 +20,16 @@
         <div>
             <h1>Zugangscodes verwalten</h1>
         </div>
-        <button type="button" class="button button--small button--primary"
-                hx-get="{{ path('app_admin_access_code_new') }}"
-                hx-target="body"
-                hx-swap="beforeend">Code hinzufügen</button>
+        <div class="flex flex-wrap gap-2">
+            <button type="button" class="button button--small button--neutral"
+                    hx-get="{{ path('app_admin_access_code_notify') }}"
+                    hx-target="body"
+                    hx-swap="beforeend">Mitarbeitende benachrichtigen</button>
+            <button type="button" class="button button--small button--primary"
+                    hx-get="{{ path('app_admin_access_code_new') }}"
+                    hx-target="body"
+                    hx-swap="beforeend">Code hinzufügen</button>
+        </div>
     </div>
 
     {% if rows is empty %}