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;
}