[cgiapp] CGI::Application::Plugin::Authentication posthook

[Terrence Brannon]

Hello, I am using CGI::Application::Plugin::Authentication and contemplating
using CGI::Application::Plugin::Authorization.

I would like some way of adding some things to $app->authen->store() after
authenticating the user, and before any runmode actually runs.

Since these things are particular to authentication, I have no need for
doing them except when a user needs to authenticate.

To be specific I want to put the user-id of the authenticated user in the
session store.