/// <summary>
/// User's next rank
/// </summary>
/// <param name="user">User to check</param>
/// <returns>Return user's next rank as Rank object</returns>
public Rank NextUserRank(User user)
{
var rankIndex = RankList.IndexOf(user.UserRank);
return(rankIndex + 1 < RankList.Count - 1 ? RankList[rankIndex + 1] : null);
}