доделал3

TravelCompany/TravelCompanyBusinessLogic/BusinessLogic/ShopLogic.cs

@@ -123,6 +123,10 @@ namespace TravelCompanyBusinessLogic.BusinessLogics
                 {
                     throw new ArgumentException($"Поставка: Товар с id:{model.TravelId} не найденн");
                 }
+                if (shop.ShopTravels.Sum(kv => kv.Value.Item2) + model.Count > shop.TravelMaxCount)
+                {
+                    throw new ArgumentException("Превышена максимальная вместимость магазина");
+                }
                 shop.ShopTravels.Add(model.TravelId, (Travel, model.Count));
             }
 
@@ -139,6 +143,7 @@ namespace TravelCompanyBusinessLogic.BusinessLogics
             return true;
         }
 
+
         private void CheckModel(ShopBindingModel model, bool withParams = true)
         {
             if (model == null)