private void renderSingularHit(XMLWriter writer, Hit hit) {
        if ( ! hit.isMeta() &&  ! writer.isIn("content"))
            writer.openTag("content");

        writer.openTag(HIT);
        renderHitAttributes(hit,writer);
        writer.closeStartTag();
        renderField(writer, "id", hit.getId());
        hit.forEachField((name, value) -> renderField(writer, name, value));
        writer.closeTag();
    }
Creates a json renderer using a custom executor.
Using a custom executor is useful for tests to avoid creating new threads for each renderer registry.
container-search/src/main/java/com/yahoo/search/pagetemplates/result/PageTemplatesXmlRenderer.java