apollo-biz/src/main/java/com/ctrip/framework/apollo/biz/entity/InstanceConfig.java/InstanceConfig/toString
class InstanceConfig:  @Override
  public String toString() {
    return MoreObjects.toStringHelper(this)
        .omitNullValues()
        .add("id", id)
        .add("configAppId", configAppId)
        .add("configClusterName", configClusterName)
        .add("configNamespaceName", configNamespaceName)
        .add("releaseKey", releaseKey)
        .add("dataChangeCreatedTime", dataChangeCreatedTime)
        .add("dataChangeLastModifiedTime", dataChangeLastModifiedTime)
        .toString();
  }