Player was able to sit down at two seats at the same time

[piggydoughnut]

Backend has to make sure it does not allow the same user to sit at two different seats.

GUI needs to hide SIT HERE from other seats once the user clicked on any SEAT.

1. User clicks on SIT HERE
2. All other seats become blank while GUI is waiting for the server response
3. Once server responds with
   3.1 seat_taken: 0 then the user takes that seat.
   3.2 seat_taken: 1 -> server pushes information on the new seats occupancy. SIT HERE appears for all the available seats.