@Override
    public boolean equals(Object o) {
        if (this == o) return true;
        if (o == null || getClass() != o.getClass()) return false;
        ClusterResource that = (ClusterResource) o;
        return Objects.equals(clusterId, that.clusterId);
    }
Return the cluster id. Note that it may be {@code null} if the metadata request was sent to a broker without
support for cluster ids. The first version of Kafka to support cluster id is 0.10.1.0.
clients/src/main/java/org/apache/kafka/common/ClusterResource.java