code: public static <T extends XMLObject> void addAttributeValue(Attribute attribute, T value) {
      attribute.getAttributeValues().add(value);
    }
docs: Utility method that adds an XML object as a value to an {@code Attribute}.
  <p>
  Example:
  </p>
  <pre>{@code
  Attribute attr =
  AttributeUtils.createAttribute("http://eidas.europa.eu/attributes/naturalperson/CurrentFamilyName", "FamilyName");
  CurrentFamilyNameType value = AttributeUtils.createAttributeValueObject(CurrentFamilyNameType.class);
  value.setValue("Lindström");
  AttributeUtils.addAttributeValue(attr, value);}
  </pre>
  
  @param <T>
  the type
  @param attribute
  the attribute to update
  @param value
  the value to add