public static ClusterMembership from(String stringValue, Version vespaVersion, Optional<DockerImage> dockerImageRepo) {
        return from(stringValue, vespaVersion, dockerImageRepo, ZoneEndpoint.defaultEndpoint);
    }
Returns all the information in this as a string which can be used to construct the same ClusterMembership
instance using {@link #from}. This string is currently stored in ZooKeeper on running instances.
config-provisioning/src/main/java/com/yahoo/config/provision/ClusterMembership.java