public X509Certificate sign(PrivateKey caPrivateKey, X509Certificate caCertificate, PKCS10CertificationRequest csr, RenewalPolicy renewalPolicy) throws Exception {
        Instant validFrom = Instant.now(clock);
        var validUntil = validFrom.plus(renewalPolicy.parsedCertificateLifetime());

        return sign(caPrivateKey, caCertificate, csr, validFrom, validUntil);
    }
@Test
    void testSigningCertWithSixMonthsLifetime() throws Exception {
        var result = sign("P6M");
        assertThat(result).isNotNull();
        assertThat(result.getNotAfter()).isEqualTo(fixedInstant.plus(180, ChronoUnit.DAYS));
    }