private static void addRoutes(String directRoute, String indexedRoute, DocumentProtocolPoliciesConfig.Cluster.Builder builder) {
            builder.defaultRoute(directRoute)
                   .route(new DocumentProtocolPoliciesConfig.Cluster.Route.Builder()
                                  .messageType(com.yahoo.documentapi.messagebus.protocol.DocumentProtocol.MESSAGE_PUTDOCUMENT)
                                  .name(indexedRoute))
                   .route(new DocumentProtocolPoliciesConfig.Cluster.Route.Builder()
                                  .messageType(com.yahoo.documentapi.messagebus.protocol.DocumentProtocol.MESSAGE_REMOVEDOCUMENT)
                                  .name(indexedRoute))
                   .route(new DocumentProtocolPoliciesConfig.Cluster.Route.Builder()
                                  .messageType(com.yahoo.documentapi.messagebus.protocol.DocumentProtocol.MESSAGE_UPDATEDOCUMENT)
                                  .name(indexedRoute));
    }
Creates a service index based on the plugins loaded. This means to fill the index with all services known by this
protocol by traversing the plugins.

@param plugins All initialized plugins of the Vespa model
@return the index of all known services
config-model/src/main/java/com/yahoo/vespa/model/routing/DocumentProtocol.java