public AvatarService(IUserRepository userRepository,
                      IFileHandler fileHandler, IImageService imageService,
                      IFileValidator fileValidator)
 {
     _userRepository = userRepository.CheckIfNotEmpty();
     _fileHandler    = fileHandler.CheckIfNotEmpty();
     _imageService   = imageService.CheckIfNotEmpty();
     _fileValidator  = fileValidator.CheckIfNotEmpty();
 }