update sku to string

src/main/java/com/ascendfinalproject/warehouse/models/Item.java

@@ -15,12 +15,12 @@ public class Item {
     private String itemName;
     private int itemQuantity;
     private float itemPrice;
-    private int itemSku;
+    private String itemSku;
 
     public Item() {
     }
 
-    public Item(String itemId, String itemName, int itemQuantity, double itemPrice, int itemSku) {
+    public Item(String itemId, String itemName, int itemQuantity, double itemPrice, String itemSku) {
         this.itemId = itemId;
         this.itemName = itemName;
         this.itemQuantity = itemQuantity;