code: static SafeHtml principalItem(final String css, final Principal principal) {
          return principal.getRealm() == null ?
                  ITEMS.item(css, principal.getName(), principal.getName()) :
                  ITEMS.principalWithRealm(css, principal.getName(),
                          principal.getName() + " (at) " + principal.getRealm(), principal.getRealm());
      }
docs: ------------------------------------------------------ principal