public string addForum(string forumName, string requestingUser)
        {
            List <string> input = new List <string>()
            {
                forumName, requestingUser
            };

            if (Constants.isValidInput(input))
            {
                lock (o)
                {
                    string res = _um.addForum(forumName, requestingUser);
                    if (res.Equals(Constants.SUCCESS))
                    {
                        return(_fm.addForum(forumName));
                    }
                    return(res);
                }
            }
            return(Constants.INVALID_INPUT);
        }