Add support for inventory timestamps

PartSource.Api/Controllers/InventoryController.cs

@@ -23,7 +23,7 @@ namespace PartSource.Api.Controllers
         [Route("sku/{sku}/storeNumber/{storeNumber}")]
         public async Task<ActionResult> GetInventory(int sku, int storeNumber)
         {
-            PartsAvailability inventory = await _inventoryService.GetInventory(sku, storeNumber);
+            PartAvailability inventory = await _inventoryService.GetInventory(sku, storeNumber);
 
             if (inventory == null)
             {
@@ -36,7 +36,8 @@ namespace PartSource.Api.Controllers
                 {
                     StoreNumber = inventory.Store,
                     Sku = sku,
-                    Quantity = inventory.QTY
+                    Quantity = inventory.QTY,
+                    Updated = inventory.Updated ?? System.DateTime.MinValue
                 }
             });
         }