protected String toStringValue() {
        return cluster.type().name() +
               "/" + cluster.id().value() +
               (cluster.group().isPresent() ? "/" + cluster.group().get().index() : "/") +
               "/" + index +
               ( cluster.isExclusive() ? "/exclusive" : "") +
               ( retired ? "/retired" : "") +
               ( cluster.isStateful() ? "/stateful" : "") +
               ( cluster.combinedId().isPresent() ? "/" + cluster.combinedId().get().value() : "");

    }
A node's membership in a cluster. This is a value object.
The format is "clusterType/clusterId/groupId/index[/exclusive][/retired][/stateful][/combinedId]"

@author bratseth
config-provisioning/src/main/java/com/yahoo/config/provision/ClusterMembership.java