private SearchChainConfig createConfig(Source source, FederationOptions targetOptions) {
            return new SearchChainConfig(source,
                                         source.getParentProvider().getComponentId(),
                                         targetOptions,
                                         source.getDocumentTypes());
        }
One or more search chains that are handled as a single group,
which can be federated to as a single entity.
config-model/src/main/java/com/yahoo/vespa/model/container/search/searchchain/FederationSearcher.java