public static String findBsnOudeWaarde(List<Container> categorieList){
        return findValue(categorieList, CATEGORIE_IDENTIFICATIENUMMERS_OUDE_WAARDE, ELEMENT_BURGERSERVICENUMMER);
    }
@Test
    public void testFindOldBsn(){assertThat(CategorieUtil.findBsnOudeWaarde(createFullCategories()), is("burgerservicenummer_oud"));}