Updated the reference flask example to include token auth

docs/source/reference/services.md

@@ -200,7 +200,9 @@ or via the `JUPYTERHUB_API_TOKEN` environment variable.
 
 Most of the logic for authentication implementation is found in the
 [`HubAuth.user_for_cookie`](services.auth.html#jupyterhub.services.auth.HubAuth.user_for_cookie)
-method, which makes a request of the Hub, and returns:
+and in the
+[`HubAuth.user_for_token`](services.auth.html#jupyterhub.services.auth.HubAuth.user_for_token)
+methods, which makes a request of the Hub, and returns:
 
 - None, if no user could be identified, or
 - a dict of the following form:
@@ -252,8 +254,11 @@ def authenticated(f):
     @wraps(f)
     def decorated(*args, **kwargs):
         cookie = request.cookies.get(auth.cookie_name)
+        token = request.headers.get(auth.auth_header_name)
         if cookie:
             user = auth.user_for_cookie(cookie)
+        elif token:
+            user = auth.user_for_token(token)
         else:
             user = None
         if user: