public IActionResult Post([FromBody] PromotionRequest promotionRequest)
        {
            if (promotionRequest == null)
            {
                return(StatusCode(400, ModelState));
            }
            if (!ModelState.IsValid)
            {
                return(StatusCode(400, ModelState));
            }

            try
            {
                var promotion = promotionRepository.CreatePromotion(promotionRequest);
                return(Ok(promotion));
            }
            catch (Exception e)
            {
                throw e;
            }
        }