Build exchange workspace and shared transaction services (#28)

frontend/app/test/localization_test.dart

@@ -83,15 +83,7 @@ void main() {
       await tester.tap(find.byKey(const ValueKey('submit')));
       await tester.pumpAndSettle();
       expect(find.text('Enter a valid email address.'), findsOneWidget);
-      await tester.ensureVisible(find.byKey(const ValueKey('locale-selector')));
-      await tester.tap(find.byKey(const ValueKey('locale-selector')));
-      await tester.pumpAndSettle();
-      await tester.tap(
-        find.ancestor(
-          of: find.text('Русский'),
-          matching: find.byType(CheckedPopupMenuItem<Locale>),
-        ),
-      );
+      await locale.setLocale(const Locale('ru'));
       await tester.pumpAndSettle();
       expect(find.text('Введите корректный адрес почты.'), findsOneWidget);
       expect(find.text('Алексей'), findsOneWidget);