private static void renderContinuation(String id, Continuation continuation, XMLWriter writer) {
        writer.openTag(TAG_CONTINUATION).attribute(TAG_CONTINUATION_ID, id).content(continuation, false).closeTag();
    }
Renders the header for the given grouping hit. If the hit is not a grouping hit, this method does nothing and
returns false.
<p>Post-condition if this is a grouping hit: The hit tag is open.

@param hit    The hit whose header to render.
@param writer The writer to render to.
@return True if the hit was rendered.
@throws IOException Thrown if there was a problem writing.
container-search/src/main/java/com/yahoo/search/grouping/result/HitRenderer.java