Config.fromJson constructor
Implementation
factory Config.fromJson(Map<String, String> json) {
  Config config = Config(
    applicationId: json['applicationId'] ?? "",
    clientId: json['clientId'] ?? "",
    clientSecret: json['clientSecret'] ?? "",
  );
  if (json["category"] != null) {
    config.category = json["category"];
  }
  return config;
}