public AddNicknamesCommand(
     INicknameService nicknameService,
     IUserExists userExists,
     IAddNicknames addNicknames)
 {
     _nicknameService = nicknameService;
     _userExists      = userExists;
     _addNicknames    = addNicknames;
 }
 public GetTheYoungestNicknameCommand(IUserExists userExists, IGetTheYoungestNickname getTheYoungestNickname)
 {
     _userExists             = userExists;
     _getTheYoungestNickname = getTheYoungestNickname;
 }