public static Slime toSlime(List<X509Certificate> certificateList) {
        Slime slime = new Slime();
        var root = slime.setObject();
        Cursor array = root.setArray(certificateField);
        toSlime(certificateList, array);
        return slime;
    }
Serializer for operator certificates.
The certificates are serialized as a list of PEM strings.
@author tokle
configserver/src/main/java/com/yahoo/vespa/config/server/tenant/OperatorCertificateSerializer.java