"before exiting" controller

**Frederic Girard** ([Bug 62264](https://bz.apache.org/bugzilla//show_bug.cgi?id=62264&redirect=false)):
As there is a "once only" controller, used for initial connections or login, it would be useful to have a "before exiting" controller, for disconnections and logout requests.

It should be used only when the thread is about to end its execution flow.

OS: All

Start by locating the existing "once only" controller and the code that ends a thread's execution flow. Trace how initial-connection or login handling is wired, then determine the design needed for a corresponding controller that runs only during disconnection or logout before the thread exits.

Written by the indexing model from the issue text.