public async Task <IActionResult> Post(Donor donor)
        {
            if (!ModelState.IsValid)
            {
                return(BadRequest());
            }

            await _aidRepository.SaveDonor(donor);

            var response = _declarationService.PrepareDeclaration(donor.DonationAmount);

            return(Ok(response));
        }
        public void PrepareDeclaration()
        {
            //Arrange
            double donationAmount = 150;
            var    expected       = new GiftAidDeclarationResponse()
            {
                DeclarationId = Guid.NewGuid(),
                GiftAidAmount = 1.875
            };

            //Act
            var actual = _declarationService.PrepareDeclaration(donationAmount);

            //Assert
            Assert.IsType <GiftAidDeclarationResponse>(actual);
            Assert.Equal(actual.GiftAidAmount, expected.GiftAidAmount);
        }