sessionDatas not reinitialized from request to request in a thread
Assume two requests from two different users are handled by the same Apache2 thread, the second user can inherit session data from the first one.
In LL::NG::Handler::Main, session datas are stored in $datas, a static hashref persistent from request to request. But $datas is never emptied. So, if user1 had a session attribute foo and user2 should not, user2 will still inherit this attribute. The bugs also concerns local macros.
I think we just have to empty $datas, but I did not understand well the trick around local macros in retrieveSession, I think it is suboptimal.