public SignedUpHandler(IHandler handler,
                        IFrequentFlyersRepository frequentFlyersRepository)
 {
     _handler = handler;
     _frequentFlyersRepository = frequentFlyersRepository;
 }
 public GetFrequentFlyerHandler(IFrequentFlyersRepository frequentFlyersRepository)
 {
     _frequentFlyersRepository = frequentFlyersRepository;
 }