private static void addContentRouting(List<ContentCluster> content, RoutingTableSpec table) {
        for (ContentCluster cluster : content) {
            RouteSpec spec = new RouteSpec(cluster.getConfigId());
            var indexingDocproc = cluster.getSearch().getIndexingDocproc();
            table.addRoute(spec.addHop("[MessageType:" + cluster.getConfigId() + "]"));
            table.addRoute(new RouteSpec(getIndexedRouteName(cluster.getConfigId()))
                                   .addHop(indexingDocproc.getServiceName())
                                   .addHop("[Content:cluster=" + cluster.getName() + "]"));
            table.addRoute(new RouteSpec(getDirectRouteName(cluster.getConfigId()))
                                   .addHop("[Content:cluster=" + cluster.getName() + "]"));
            table.addRoute(new RouteSpec("storage/cluster." + cluster.getName())
                                   .addHop("route:" + cluster.getConfigId()));
        }
    }
Create hops to all configured storage nodes for the Document protocol. The "Distributor" policy resolves its
recipients using slobrok lookups, so it requires no configured recipients.

@param content the storage model from {@link com.yahoo.vespa.model.VespaModel}
@param table   the routing table to add to
config-model/src/main/java/com/yahoo/vespa/model/routing/DocumentProtocol.java