private function addCommonHeaders(Request $request, Response $response)
    {
        // replace content-type if a schema was requested
        if ($request->attributes->get('schemaRequest')) {
            $response->headers->set('Content-Type', 'application/schema+json');
        }

        if ($request->attributes->has('recordCount')) {
            $response->headers->set(
                'X-Record-Count',
                (string) $request->attributes->get('recordCount')
            );
        }

        // search source header?
        if ($request->attributes->has('X-Search-Source')) {
            $response->headers->set(
                'X-Search-Source',
                (string) $request->attributes->get('X-Search-Source')
            );
        }
    }