public ActionResult AddVersion(VersionViewModel version)
        {
            string error = null;
            if(TryValidateModel(version))
            {
                Product product = _productRepository.Find(version.ProductId);
                product.Versions.Add(new Version { Name = version.Name, IamRole = version.IamRole});
                _productRepository.Update(product);
            }
            else
            {
                error = ModelState.SelectMany(x => x.Value.Errors).First().ErrorMessage;
            }

            return RedirectToAction("Index", new {productId = version.ProductId, error});
        }
        public ActionResult AddVersion(Guid productId, string error = null)
        {
            if(error != null)
            {
                ModelState.AddModelError("", error);
            }

            var model = new VersionViewModel {ProductId = productId};
            return View(model);
        }