Submit customer identity proofs and show reviewed limits

frontend/packages/sxchnge_kyc/test/onboarding_test.dart

@@ -0,0 +1,41 @@
+import 'package:flutter_test/flutter_test.dart';
+
+import 'package:sxchnge_kyc/sxchnge_kyc.dart';
+
+class RealIdentity extends DummyIdentityService {
+  IdentityStatus status = IdentityStatus.unverified;
+  bool unavailable = false;
+  @override
+  bool get isSimulated => false;
+  @override
+  Future<Identity> fetch() async {
+    if (unavailable) throw const KycException(KycError.unavailable);
+    return Identity(status: status);
+  }
+}
+
+void main() {
+  test('offers optional verification once to a basic customer and allows later corrections', () async {
+    final service = RealIdentity(),
+        provider = IdentityOnboardingProvider(RealIdentity());
+    expect(await provider.offer('customer'), true);
+    expect(await provider.offer('customer'), false);
+    final subject = IdentityOnboardingProvider(service);
+    service.status = IdentityStatus.pending;
+    expect(await subject.offer('pending'), false);
+    service.status = IdentityStatus.approved;
+    expect(await subject.offer('approved'), false);
+    service.status = IdentityStatus.changesRequested;
+    expect(await subject.offer('correction'), true);
+  });
+  test(
+    'a failed optional identity dependency never blocks basic login',
+    () async {
+      final service = RealIdentity()..unavailable = true;
+      expect(
+        await IdentityOnboardingProvider(service).offer('customer'),
+        false,
+      );
+    },
+  );
+}