Change unauthorized message if no UI is installed

This "Unauthorized" message has been a constant source of confusion for
users that forget to install a UI.  This commit updates the message to
be more clear, and present users with some hints that they have
forgotten to install a webui if they expected the auth to succeed.

Tested: String change only.  Code compiles.

Signed-off-by: Ed Tanous <edtanous@google.com>
Change-Id: Ic68e4622082caf5e32e496ec56f0c8b409b91990
diff --git a/include/forward_unauthorized.hpp b/include/forward_unauthorized.hpp
index 9ba2b1c..5d5e744 100644
--- a/include/forward_unauthorized.hpp
+++ b/include/forward_unauthorized.hpp
@@ -34,7 +34,8 @@
         // If we don't have a webui installed, just return an unauthorized
         // body
         res.result(boost::beast::http::status::unauthorized);
-        res.body() = "Unauthorized";
+        res.body() =
+            "No authentication provided, and no login UI present to forward to.";
         return;
     }