code: public String getPageSufix() {
          if(has(pageSuffix)) {
              return pageSuffix;
          }
          if(!has(indexPage) && !has(loginPage)) {
              pageSuffix = Constants.DEFAULT_PAGE_FORMAT;
          }
          if(has(indexPage)) {
              pageSuffix = indexPage.substring(indexPage.lastIndexOf('.')+1);
          } else {
              pageSuffix = indexPage.substring(loginPage.lastIndexOf('.')+1);
          }
          return pageSuffix;
      }
docs: infer page suffix from index and login page configured in admin-config.properties
  
  If none is configured then use default suffix: 'xhtml'.