Previously, userid was generated by the "/login" route and passed along.
This commit completely removes the uuid "userid" (and disables the LoginController too and any Jwt check).
"userid" is replaced by the "socket id" of the connection.
So a user is now identified using a socket id, which is unique for a given connection.
So far, someone joining a map would not see the circles of groups already formed until someone moves in the group (because the "circle_moved_or_updated" event was not fired when someone arrives)
This commit fixes this behaviour. Someone entering a room will receive an event for each and every group currently formed.
This PR adds the display of a circle around groups. This is useful to view where you need to go to speak to someone but also to debug.
Note: implementation is suboptimal, relying on a "graphics" object that is known to be slow. In the future, we need to use a circle as a sprite instead.
