TF-46 Create object, builder for model and core module

model/lib/extensions/utcdate_extension.dart

@@ -0,0 +1,13 @@
+import 'package:intl/intl.dart';
+import 'package:jmap_dart_client/jmap/core/utc_date.dart';
+
+extension UTCDateExtension on UTCDate? {
+
+  String formatDate({String pattern = 'yMMMd', String locale = 'en_US'}) {
+    if (this != null) {
+      return DateFormat(pattern, locale).format(this!.value);
+    } else {
+      return '';
+    }
+  }
+}