public ZooKeeperRegistrationSpec build() {
        final ServerSetsInstance serverSetsInstance =
                new ServerSetsInstance(serviceEndpoint, additionalEndpointsBuilder.build(),
                                       shardId, metadata);
        return new ServerSetsRegistrationSpec(nodeName, sequential, serverSetsInstance);
    }
Returns a newly-created {@link ZooKeeperRegistrationSpec} based on the properties set so far.
zookeeper3/src/main/java/com/linecorp/armeria/server/zookeeper/ServerSetsRegistrationSpecBuilder.java