+# AuthHandler allows access to session user
+#
+# Inherit this handler to access to session user from your custom handler.
+#
+# For example, you need a profile handler that checks if the user is logged
+# before returning it in json format.
+# ~~~
+# import popcorn::pop_auth
+#
+# class ProfileHandler
+# super AuthHandler
+#
+# redef fun get(req, res) do
+# var user = check_session_user(req, res)
+# if user == null then return
+# res.json user
+# end
+# end
+# ~~~
+#
+# By using `check_session_user`, we delegate to the `AuthHandler` the responsability
+# to set the HTTP 403 error.
+# We then check is the user is not null before pursuing.
+abstract class AuthHandler