void updateGroupLightstateRTC(String json) {
  StaticJsonDocument<512> doc;
  DeserializationError error = deserializeJson(doc, json);
  if (error) {
    Serial.print(F("deserializeJson() failed: "));
    Serial.println(error.c_str());
    return;
  } else {
    JsonObject lightstates = doc["lightstates"];
    for (x = 0; x < lightstates.size(); x++) {
      //?
    }
  }
}