Add reusable two-factor verification for login and money operations (#32)

frontend/app/lib/main.dart

@@ -31,6 +31,7 @@ class SxchngeApp extends StatefulWidget {
     this.identityService,
     this.limitsService,
     this.walletService,
+    this.twoFactorService,
     this.photoService = const FilePhotoService(),
     this.loginService = const DummyLoginService(),
     this.signupService = const DummySignupService(),
@@ -41,6 +42,7 @@ class SxchngeApp extends StatefulWidget {
   final IdentityService? identityService;
   final LimitsService? limitsService;
   final WalletService? walletService;
+  final TwoFactorService? twoFactorService;
   final PhotoService photoService;
   final LoginService loginService;
   final SignupService signupService;
@@ -54,11 +56,21 @@ class _SxchngeAppState extends State<SxchngeApp> {
   late final _locale = widget.localeProvider ?? LocaleProvider();
 
   late final _analytics = widget.analyticsService ?? DummyAnalyticsService();
+  late final _factors = widget.twoFactorService ?? DummyTwoFactorService();
+  late final _security = SecurityProvider(_factors, _analytics);
   late final _identity = widget.identityService ?? DummyIdentityService();
   late final _walletService =
       widget.walletService ??
-      DummyWalletService(_identity, initialLocale: _locale.locale.languageCode);
-  late final _wallet = WalletProvider(_walletService, _analytics);
+      DummyWalletService(
+        _identity,
+        initialLocale: _locale.locale.languageCode,
+        factors: _factors,
+      );
+  late final _wallet = WalletProvider(
+    _walletService,
+    _analytics,
+    factors: _factors,
+  );
   late final _limits =
       widget.limitsService ??
       (_walletService is DummyWalletService
@@ -67,7 +79,7 @@ class _SxchngeAppState extends State<SxchngeApp> {
   late final _journeys = JourneyRecorder(_analytics);
   late final _services = InstrumentedAuthServices(
     recorder: _journeys,
-    loginService: widget.loginService,
+    loginService: GuardedLoginService(widget.loginService, _factors),
     signupService: widget.signupService,
     verificationService: widget.verificationService,
   );
@@ -83,7 +95,7 @@ class _SxchngeAppState extends State<SxchngeApp> {
 
   void _routeChanged() {
     final path = _router.routeInformationProvider.value.uri.path;
-    if (path == '/' && _previousPath != '/') {
+    if (path == '/' && _previousPath != '/' && _previousPath != '/two-factor') {
       _journeys.abandon(JourneyExit.navigation);
     }
     _previousPath = path;
@@ -95,6 +107,7 @@ class _SxchngeAppState extends State<SxchngeApp> {
     _router.dispose();
     _journeys.dispose();
     _wallet.dispose();
+    _security.dispose();
     _locale.dispose();
     super.dispose();
   }
@@ -103,6 +116,8 @@ class _SxchngeAppState extends State<SxchngeApp> {
   Widget build(BuildContext context) => MultiProvider(
     providers: [
       ChangeNotifierProvider.value(value: _wallet),
+      ChangeNotifierProvider.value(value: _security),
+      Provider<TwoFactorService>.value(value: _factors),
       Provider<JourneyRecorder>.value(value: _journeys),
       Provider<AnalyticsService>.value(value: _analytics),
       Provider<IdentityService>.value(value: _identity),