docs: public String validationErrors() {
  
          List<String> errors = new ArrayList<>();
          for (File config : getConfigFiles()) {
              String filename = config.getName();
              try (FileInputStream stream = new FileInputStream(config)) {
                  CmsXmlUtils.unmarshalHelper(CmsFileUtil.readFully(stream, false), new CmsXmlEntityResolver(null), true);
              } catch (CmsXmlException e) {
                  errors.add(filename + ":" + e.getCause().getMessage());
              } catch (Exception e) {
                  errors.add(filename + ":" + e.getMessage());
              }
          }
          if (errors.size() == 0) {
              return null;
          }
          String errString = CmsStringUtil.listAsString(errors, "\n");
          JSONObject obj = new JSONObject();
          try {
              obj.put("err", errString);
          } catch (JSONException e) {
  
          }
          return obj.toString();
      }