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

frontend/packages/sxchnge_wallet/lib/src/providers/wallet.dart

@@ -4,12 +4,15 @@ import 'package:flutter/foundation.dart';
 
 import 'package:sxchnge_analytics/sxchnge_analytics.dart';
 
+import 'package:sxchnge_auth/sxchnge_auth.dart';
+
 import '../models/wallet.dart';
 import '../services/contracts.dart';
 
 class WalletProvider extends ChangeNotifier {
-  WalletProvider(this.service, this.analytics);
+  WalletProvider(this.service, this.analytics, {this.factors});
   final WalletService service;
+  final TwoFactorService? factors;
   final AnalyticsService analytics;
   WalletSnapshot? data;
   bool loading = false,