public static void addDefaultLocalProviders(SearchChains searchChains, Set<String> clusterNames) {
        Set<String> missingClusters = new LinkedHashSet<>(clusterNames);
        missingClusters.removeAll(presentClusters(searchChains));

        for (String clusterName : missingClusters) {
            searchChains.add(createDefaultLocalProvider(clusterName));
        }
    }
Adds default search chains for all local clusters not mentioned explicitly
@author Tony Vaagenes
config-model/src/main/java/com/yahoo/vespa/model/container/search/searchchain/defaultsearchchains/LocalClustersCreator.java