apollo-portal/src/main/java/com/ctrip/framework/apollo/portal/component/emailbuilder/GrayPublishEmailBuilder.java/GrayPublishEmailBuilder/emailContent
class GrayPublishEmailBuilder:  @Override
  public String emailContent(Env env, ReleaseHistoryBO releaseHistory) {
    String result = renderEmailCommonContent(env, releaseHistory);
    return renderGrayReleaseRuleContent(result, releaseHistory);
  }