docs: public static void addUnspecifiedAttributes(FeatureDescriptor descriptor, 
              Tag tag, String[] standardAttributesSorted, FaceletContext ctx)
      {
          for (TagAttribute attribute : tag.getAttributes().getAll())
          {
              final String name = attribute.getLocalName();
              if (Arrays.binarySearch(standardAttributesSorted, name) < 0)
              {
                  // attribute not found in standard attributes
                  // --> put it on the BeanDescriptor
                  descriptor.setValue(name, attribute.getValueExpression(ctx, Object.class));
              }
          }
      }