/// <summary>
 /// Adds a user to the group. The group must have the SiteId in order to do this operation
 /// </summary>
 /// <param name="userToAdd">User to add to the group</param>
 /// <returns></returns>
 public User AddUser(User userToAdd)
 {
     return AddUser(userToAdd.Id);
 }
 /// <summary>
 /// 
 /// </summary>
 /// <param name="currentUser"></param>
 /// <returns></returns>
 public bool IsInGroup(User currentUser)
 {
     return this.IsInGroup(currentUser.Id);
 }