private async Task <Validation <Error, Course> > Validate(CreateCourse create) =>
 (await DepartmentMustExist(create), ValidateTitle(create))
 public Task <Either <Error, int> > Handle(CreateCourse request, CancellationToken cancellationToken) =>
 Validate(request)
 .MapT(PersistCourse)
 .Bind(v => v.ToEitherAsync());