Display "batch code" for stock item

.gitmodules

@@ -1,3 +1,3 @@
 [submodule "lib/l10n"]
 	path = lib/l10n
-	url = https://github.com/inventree/inventree-app-i18n
+	url = git@github.com:SchrodingersGat/inventreeapp.git

lib/inventree/stock.dart

@@ -220,6 +220,8 @@ class InvenTreeStockItem extends InvenTreeModel {
 
   int get status => jsondata['status'] ?? -1;
 
+  String get batch => jsondata["batch"] ?? "";
+
   int get partId => jsondata['part'] ?? -1;
   
   String get purchasePrice => jsondata['purchase_price'] ?? "";

lib/widget/stock_detail.dart

@@ -458,6 +458,16 @@ class _StockItemDisplayState extends RefreshableState<StockDetailWidget> {
       );
     }
 
+    if (item.batch.isNotEmpty) {
+      tiles.add(
+        ListTile(
+          title: Text(L10().batchCode),
+          subtitle: Text(item.batch),
+          leading: FaIcon(FontAwesomeIcons.layerGroup),
+        )
+      );
+    }
+
     // Last update?
     var update_date = item.updatedDateString;