public ShoppingListCreator AddItems(ShoppingListAdder adder)
 {
     this.addQueue.Add(adder);
     return this;
 }
 public static ShoppingListAddAction Create()
 {
     var adder = new ShoppingListAdder();
     return new ShoppingListAddAction(adder);
 }
 public ShoppingListAddAction(ShoppingListAdder adder)
 {
     this.adder = adder;
 }