public IActionResult SaveNewsLetter(NewsLetterViewModel newsLetterVm)
        {
            if (!ModelState.IsValid)
            {
                return(new OkObjectResult(false));
            }

            if (newsLetterVm.Id != 0)
            {
                _newsLetterService.UpdateNewsLetter(newsLetterVm);
            }
            else
            {
                _newsLetterService.AddNewsLetter(newsLetterVm);
            }

            _newsLetterService.Save();
            return(new OkObjectResult(true));
        }