public void Generated_code_should_be_unique()
        {
            // act
            var service = new RegistrationCodeService(serviceContext);
            var code1   = service.CreateCode(Username, UserId, CurrentDate);
            var code2   = service.CreateCode(Username, UserId, CurrentDate.AddMilliseconds(1));

            // assert
            code1.Should().NotBe(code2);
        }