answerChallenge method
Process the challenge
sent by the server and return a String response
Implementation
@override
String answerChallenge(String? challenge) {
// Encode as a able
TypeEncoder encoder = TypeEncoder();
encoder.writeFieldTable({"LOGIN": userName, "PASSWORD": password});
// The spec defines the challenge response as a string (with its own length as a prefix). We
// need to skip the table length from our response so the length does not get written twice
Uint8List res = encoder.writer.joinChunks();
return String.fromCharCodes(Uint8List.view(res.buffer, 4));
}