generateGameID function
Implementation
GameCode generateGameID(List<String> avoidList) {
var gameid = '';
while (gameid.length != 4 || avoidList.contains(gameid)) {
gameid = ('BCDFGHJKLMNPQRSTVWXZ'.characters.toList()..shuffle())
.join()
.substring(0, 4);
}
return gameid;
}