decodeData method
Implementation
@override
JWTData decodeData(Uint8List data) {
  final List<String> params = utf8.decode(data).split(JWT_DELIMITER);
  JWTHeader header = JWTHeader.fromJson(jsonDecode(params[0]));
  JWTPayload payload = JWTPayload.fromJson(jsonDecode(params[1]));
  return JWTData(header, payload);
}