private Validation <ValidationError, Subscription> Validate(Unsubscribe request) =>
 (Helpers.SubscriberMustBeValid(request.Subscriber), Helpers.IdListMustHaveElements(request.AnimeId))
 public Task <Either <DomainError, Unit> > Handle(Unsubscribe request, CancellationToken cancellationToken)
 {
     return(Validate(request)
            .ToEither(nameof(Unsubscribe))
            .BindAsync(RemoveSubscription));
 }