apollo-common/src/main/java/com/ctrip/framework/apollo/common/entity/BaseEntity.java/BaseEntity/toStringHelper
class BaseEntity:  protected ToStringHelper toStringHelper() {
    return MoreObjects.toStringHelper(this).omitNullValues().add("id", id)
        .add("dataChangeCreatedBy", dataChangeCreatedBy)
        .add("dataChangeCreatedTime", dataChangeCreatedTime)
        .add("dataChangeLastModifiedBy", dataChangeLastModifiedBy)
        .add("dataChangeLastModifiedTime", dataChangeLastModifiedTime);
  }