update announcement

jupyterhub_custom_config.json

@@ -935,9 +935,9 @@
     }
   },
   "announcement": {
-    "show": false,
-    "title": "UNICORE maintenance 16.11.2023 08:30 - 09:30 (CET)",
-    "body": "UNICORE will be updated to the latest version. Start / Stop of JupyterLabs on HPC-Systems will not work (<a href=\"https://status.jsc.fz-juelich.de/services/41\">more</a>)."
+    "show": true,
+    "title": "Jupyter-JSC maintenance 05.12.2023 07:30 - 12:00 (CET)",
+    "body": "Unity-IdM, the authentication service, will be updated. Jupyter-JSC will be in maintenance until the update is complete (<a href=\"https://status.jsc.fz-juelich.de/services/40\">more</a>)."
   },
   "additional_spawn_options": {
     "extensions": {