Secure storage should set IOSAccessibility accessibility

[HannesVDB]

IOSAccessibility accessibility is ignored for the secure storage

class SecureStorage extends SecureStoring {
  final FlutterSecureStorage _storage;
  final iOSOptions = IOSOptions(accessibility: IOSAccessibility.first_unlock);
  SecureStorage(this._storage);
  @override
  Future<void> deleteAll() {
    return _storage.deleteAll(iOptions: iOSOptions);
  }
  @override
  Future<void> write({@required String key, @required String value}) {
    return _storage.write(key: key, value: value, iOptions: iOSOptions);
  }
  @override
  Future<String> read({@required String key}) {
    return _storage.read(key: key, iOptions: iOSOptions);
  }
  @override
  Future<void> delete({@required String key}) {
    return _storage.delete(key: key, iOptions: iOSOptions);
  }
}

[vanlooverenkoen]

We had an issue where our app was working fine when in the foreground & in the background. But as soon as your phone was locked. you couldn't access the keychain anymore on iOS.

[vanlooverenkoen]

This issue was found while debugging icapps/flutter-background-location-tracker#25