public Builder distributionConfig(DistributionConfigBundle config) {
            this.distributionConfig = config;
            return this;
        }
Feed blocking status of the entire cluster that will be communicated to the nodes
as part of the cluster state bundle. If not present, or if blockFeedInCluster is
false, feed is not automatically blocked.

Note that feed blocking only applies to client feed, not to feed generated by internal
maintenance operations such as merging.

Immutable, so may be safely passed around.
clustercontroller-core/src/main/java/com/yahoo/vespa/clustercontroller/core/ClusterStateBundle.java