Start to display user groups

lib/ui/widgets/group_icon_widget.dart

@@ -0,0 +1,50 @@
+import 'package:cached_network_image/cached_network_image.dart';
+import 'package:comunic/models/group.dart';
+import 'package:flutter/material.dart';
+
+/// Custom group icon
+///
+/// @author Pierre Hubert
+class GroupIcon extends StatelessWidget {
+  final Group group;
+  final double width;
+
+  const GroupIcon({
+    Key key,
+    @required this.group,
+    this.width = 50,
+  })  : assert(group != null),
+        assert(width != null),
+        super(key: key);
+
+  @override
+  Widget build(BuildContext context) {
+    return Material(
+      child: CachedNetworkImage(
+        imageUrl: group.iconURL,
+        width: width,
+        height: width,
+        placeholder: (c, s) => Container(
+          color: Colors.grey,
+          width: width,
+          height: width,
+          child: Padding(
+            padding: const EdgeInsets.all(8.0),
+            child: CircularProgressIndicator(
+              strokeWidth: 4.0,
+            ),
+          ),
+        ),
+        errorWidget: (c, s, o) => Container(
+          color: Colors.red,
+          width: width,
+          height: width,
+          child: Icon(
+            Icons.error,
+            color: Colors.white,
+          ),
+        ),
+      ),
+    );
+  }
+}

lib/ui/widgets/navbar_widget.dart

@@ -15,6 +15,7 @@ enum BarCallbackActions {
   OPEN_NEWEST_POSTS,
   OPEN_FRIENDS,
   OPEN_MY_PAGE,
+  OPEN_GROUPS,
   OPEN_APP_SETTINGS,
   NONE,
   ACTION_LOGOUT
@@ -81,6 +82,7 @@ final _menuItems = <_MenuItem>[
 final _menuActionsItem = <_ActionMenuItem>[
   _ActionMenuItem(
       label: tr("My Page"), action: BarCallbackActions.OPEN_MY_PAGE),
+  _ActionMenuItem(label: tr("Groups"), action: BarCallbackActions.OPEN_GROUPS),
   _ActionMenuItem(
       label: tr("App settings"), action: BarCallbackActions.OPEN_APP_SETTINGS),
   _ActionMenuItem(