TF-675 Add UploadController to handle upload attachment

lib/features/upload/presentation/extensions/list_upload_file_state_extension.dart

@@ -0,0 +1,13 @@
+import 'package:tmail_ui_user/features/upload/presentation/model/upload_file_state.dart';
+
+extension ListUploadFileStateExtension on List<UploadFileState> {
+
+  num get totalSize {
+    if (isNotEmpty) {
+      final currentListSize = map((file) => file.fileSize).toList();
+      final totalSize = currentListSize.reduce((sum, size) => sum + size);
+      return totalSize;
+    }
+    return 0;
+  }
+}