code: static X509Certificate selfSignedCertificate() throws CertificateException {
          return (X509Certificate) SslContext.X509_CERT_FACTORY.generateCertificate(
                  new ByteArrayInputStream(CERT.getBytes(CharsetUtil.US_ASCII))
          );
      }
docs: Returns a self-signed {@link X509Certificate} for {@code netty.io}.