Revert "Flush users when disconnected"

This reverts commit bc2d20ce222ffb0ca00977a5fddf845d53289622.
Revert "Revert "Flush users when disconnected""

This reverts commit 35b599fe9002396e37d61d691a5b921fc5673037.
Merge branch 'develop' of https://github.com/ChatSystem-INSA/ChatSystem into develop