protected AuthnContextClassRef buildAuthnContextClassRef(final String authnContextClassRef) {
        val classRef = new AuthnContextClassRefBuilder().buildObject();
        classRef.setURI(authnContextClassRef);
        return classRef;
    }
<p>buildAuthnContextClassRef.</p>

@param authnContextClassRef a {@link String} object
@return a {@link AuthnContextClassRef} object
pac4j-saml/src/main/java/org/pac4j/saml/sso/impl/SAML2AuthnRequestBuilder.java