public async Task <IActionResult> AddProduct([FromRoute] int id, [FromRoute] int idp)
        {
            if (!ModelState.IsValid)
            {
                return(BadRequest(ModelState));
            }

            var collection = await collectionRepository.AddCollectionProduct(id, idp);

            if (collection == null)
            {
                return(BadRequest());
            }

            CollectionDTO dto = new CollectionDTO();

            dto.CollectionId       = collection.CollectionId;
            dto.collectionName     = collection.collectionName;
            dto.aestheticParameter = collection.aestheticParameter;
            dto.products           = new List <ProductDTO>();
            foreach (CollectionProduct cp in collection.CollectionProducts)
            {
                ProductDTO pdto = productToDTO(cp.Product);
                dto.products.Add(pdto);
            }

            return(Ok(dto));
        }