multiple dining sessions are allowed for the same user.
Here is what we should do
If User A request a dining session
Scan through all the dining sessions to see if User A exists. If User A exists send him the ID of the dining session he is currently in.
If the user does not exist then check if there is an ID for that table number. If there is already a dining session with that table number then add that user to that dining session. Save the dining session and send that dining session id back to new User A
multiple dining sessions are allowed for the same user.
Here is what we should do
If User A request a dining session