Add function to open a link

- Does not seem to actually ... work.. yet

lib/inventree/model.dart

@@ -3,6 +3,7 @@ import 'dart:async';
 import 'package:InvenTree/api.dart';
 import 'package:InvenTree/widget/dialogs.dart';
 import 'package:flutter/cupertino.dart';
+import 'package:url_launcher/url_launcher.dart';
 
 import 'dart:convert';
 
@@ -54,6 +55,19 @@ class InvenTreeModel {
   // Legacy API provided external link as "URL", while newer API uses "link"
   String get link => jsondata['link'] ?? jsondata['URL'] ?? '';
 
+  void openLink() async {
+
+    if (link.isNotEmpty) {
+      print("Opening link: ${link}");
+
+      if (await canLaunch(link)) {
+        await launch(url);
+      } else {
+        // TODO
+      }
+    }
+  }
+
   String get keywords => jsondata['keywords'] as String ?? '';
 
   // Create a new object from JSON data (not a constructor!)

lib/widget/category_display.dart

@@ -267,6 +267,7 @@ class PartList extends StatelessWidget {
     return ListTile(
       title: Text("${part.name}"),
       subtitle: Text("${part.description}"),
+      trailing: Text("${part.inStock}"),
       leading: InvenTreeAPI().getImage(
         part.thumbnail,
         width: 40,

lib/widget/part_detail.dart

@@ -1,17 +1,18 @@
 
+import 'package:flutter/cupertino.dart';
+import 'package:flutter/foundation.dart';
+import 'package:flutter/material.dart';
+
+import 'package:font_awesome_flutter/font_awesome_flutter.dart';
+import 'package:url_launcher/url_launcher.dart';
+
 import 'package:InvenTree/inventree/part.dart';
 import 'package:InvenTree/widget/category_display.dart';
 import 'package:InvenTree/widget/dialogs.dart';
 import 'package:InvenTree/widget/fields.dart';
 import 'package:InvenTree/widget/part_stock_detail.dart';
-import 'package:flutter/cupertino.dart';
-import 'package:flutter/foundation.dart';
-import 'package:flutter/material.dart';
-
 import 'package:InvenTree/api.dart';
 import 'package:InvenTree/widget/refreshable_state.dart';
-import 'package:InvenTree/widget/drawer.dart';
-import 'package:font_awesome_flutter/font_awesome_flutter.dart';
 
 class PartDetailWidget extends StatefulWidget {
 
@@ -268,7 +269,9 @@ class _PartDisplayState extends RefreshableState<PartDetailWidget> {
             title: Text("${part.link}"),
             leading: FaIcon(FontAwesomeIcons.link),
             trailing: Text(""),
-            onTap: null,
+            onTap: () {
+              part.openLink();
+            },
           )
       );
     }