handle method
Implementation
@override
Future<Map<String, T>> handle(Context context, data) async {
final value = OvO.cast<Map<String, dynamic>>(data,
message: message, path: context.path);
final result = <String, T>{};
for (final (key, schema) in properties.indexed) {
result[key] = await schema.handle(context.child(key), value[key]);
}
return result;
}