initialize page_config from settings

notebook/app.py

@@ -32,8 +32,8 @@ class NotebookBaseHandler(ExtensionHandlerJinjaMixin, ExtensionHandlerMixin, Jup
         config = LabConfig()
         app = self.extensionapp
         base_url = self.settings.get("base_url")
-
-        page_config = {
+        page_config = self.settings.setdefault("page_config_data", {})
+        page_config.update({
             "appVersion": version,
             "baseUrl": self.base_url,
             "terminalsAvailable": self.settings.get("terminals_available", False),
@@ -42,7 +42,7 @@ class NotebookBaseHandler(ExtensionHandlerJinjaMixin, ExtensionHandlerMixin, Jup
             "frontendUrl": ujoin(self.base_url, "/"),
             "exposeAppInBrowser": app.expose_app_in_browser,
             "collaborative": app.collaborative,
-        }
+        })
 
         if "hub_prefix" in app.serverapp.tornado_settings:
             tornado_settings = app.serverapp.tornado_settings