Add authenticated decorator to handlers in doc

Author: fcollonval

docs/source/developers/extensions.rst

@@ -27,12 +27,15 @@ The easiest way to add endpoints and handle incoming requests is to subclass the
 .. code-block:: python
 
     from jupyter_server.base.handlers import JupyterHandler
+    import tornado
 
     class MyExtensionHandler(JupyterHandler):
 
+        @tornado.web.authenticated
         def get(self):
             ...
 
+        @tornado.web.authenticated
         def post(self):
             ...
 
@@ -178,13 +181,16 @@ Jupyter Server provides a convenient mixin class for adding these properties to
 
     from jupyter_server.base.handlers import JupyterHandler
     from jupyter_server.extension.handler import ExtensionHandlerMixin
+    import tornado
 
 
     class MyExtensionHandler(ExtensionHandlerMixin, JupyterHandler):
 
+        @tornado.web.authenticated
         def get(self):
             ...
 
+        @tornado.web.authenticated
         def post(self):
             ...
 
@@ -217,16 +223,19 @@ Pair the example above with ``ExtensionHandlers`` that also inherit the ``Extens
         ExtensionHandlerMixin,
         ExtensionHandlerJinjaMixin
     )
+    import tornado
 
     class MyExtensionHandler(
         ExtensionHandlerMixin,
         ExtensionHandlerJinjaMixin,
         JupyterHandler
     ):
 
+        @tornado.web.authenticated
         def get(self):
             ...
 
+        @tornado.web.authenticated
         def post(self):
             ...