Добавлена возможность добавлять изделия в магазин

ConfectionaryBusinessLogic/ShopLogic.cs

@@ -115,6 +115,10 @@ namespace ConfectioneryBusinessLogic
             {
                 throw new ArgumentNullException(nameof(model));
             }
+            if (count <= 0)
+            {
+                throw new ArgumentException("Количество добавляемого изделия должно быть больше 0", nameof(count));
+            }
             _logger.LogInformation("AddPastryInShop. ShopName:{ShopName}.Id:{ Id}",
                 model.Name, model.Id);
             var element = _shopStorage.GetElement(model);
@@ -125,7 +129,22 @@ namespace ConfectioneryBusinessLogic
             }
             _logger.LogInformation("AddPastryInShop find. Id:{Id}", element.Id);
 
-            return element.Pastries.TryAdd(pastry.Id, (pastry, count));
+            
+            if (element.Pastries.TryGetValue(pastry.Id, out var pair))
+            {
+                pair.Item2 += count;
+                _logger.LogInformation(
+                    "AddPastryInShop. Has been added {count} {pastry} in {ShopName}", 
+                    count, pastry.PastryName, element.Name);
+            }
+            else
+            {
+                element.Pastries[pastry.Id] = (pastry, count);
+                _logger.LogInformation(
+                    "AddPastryInShop. Has been added {count} new Pastry {pastry} in {ShopName}", 
+                    count, pastry.PastryName, element.Name);
+            }
+            return true;
         }
     }
 }