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

frontend/packages/sxchnge_wallet/lib/src/services/contracts.dart

@@ -6,7 +6,11 @@ abstract interface class WalletService {
   Future<Quote> quote(TransferRequest request);
 
   /// Same key must reconcile uncertain submissions without duplicate execution.
-  Future<WalletOperation> submit(String quoteId, String idempotencyKey);
+  Future<WalletOperation> submit(
+    String quoteId,
+    String idempotencyKey, {
+    String? approval,
+  });
   Future<WalletOperation?> findSubmission(String idempotencyKey);
   Future<AccountProfile> profile();
   Future<AccountProfile> saveLocale(String locale);

frontend/packages/sxchnge_wallet/lib/src/services/dummy.dart

@@ -1,5 +1,7 @@
 import 'dart:math';
 
+import 'package:sxchnge_auth/sxchnge_auth.dart';
+
 import 'package:sxchnge_kyc/limits_transport.dart';
 import 'package:sxchnge_kyc/sxchnge_kyc.dart';
 
@@ -11,6 +13,7 @@ import 'contracts.dart';
 class DummyWalletService implements WalletService {
   DummyWalletService(
     this.identity, {
+    this.factors,
     this.delay = const Duration(milliseconds: 350),
     this.settlement = const Duration(seconds: 2),
     DateTime Function()? now,
@@ -18,6 +21,7 @@ class DummyWalletService implements WalletService {
   }) : now = now ?? DateTime.now,
        _locale = initialLocale;
   final IdentityService identity;
+  final TwoFactorService? factors;
   final Duration delay, settlement;
   final DateTime Function() now;
   final _accounts = [
@@ -159,13 +163,28 @@ class DummyWalletService implements WalletService {
   }
 
   @override
-  Future<WalletOperation> submit(String quoteId, String idempotencyKey) async {
+  Future<WalletOperation> submit(
+    String quoteId,
+    String idempotencyKey, {
+    String? approval,
+  }) async {
     await _wait();
     if (_submissions.containsKey(idempotencyKey))
       return WalletMapper.operation(_submissions[idempotencyKey]!);
     final q = _quotes[quoteId];
     if (q == null) throw const WalletException(WalletError.expiredQuote);
     final verified = await _verified();
+    try {
+      await factors?.authorize(
+        FactorPurpose.values.byName(q.request.kind),
+        q.id,
+        approval,
+      );
+    } catch (_) {
+      final accepted = _submissions[idempotencyKey];
+      if (accepted != null) return WalletMapper.operation(accepted);
+      rethrow;
+    }
     _settle();
     if (_submissions.containsKey(idempotencyKey))
       return WalletMapper.operation(_submissions[idempotencyKey]!);