Several active sessions per user

For now, FeedbackUsers can't have several active sessions at the same time because they just have a single pointer Session *active_session. However, there are cases where a User can have several active sessions at the same time

TODO:

  • create an example highlighting the possibility of having several simultaneous active sessions
  • add it to the test suite
  • change the implem of FeedbackUser to take that case into account
Edited by Ghost User