Typically query parameters get mapped to optional variables in dart lang using rpc.
For example http://www.exampleurl.com/test?filter=1
Future test({int filter})
Gets mapped to filter.
However if it is http://www.exampleurl.com/test?hub.challenge=1. There appears to be no way to retrieve that query parameter. This is significant because it's required for verification with Facebook's Messenger API.
