@Override
    public void process(final HttpRequest request,
                        final EntityDetails entity,
                        final HttpContext context) throws HttpException, IOException {
        final ProtocolVersion protocolVersion = context.getProtocolVersion();
        request.addHeader(HttpHeaders.VIA, ViaCacheGenerator.INSTANCE.lookup(protocolVersion));
    }
This response interceptor adds {@literal VIA} header to all outgoing
request messages dispatched through the caching layer.
httpclient5-cache/src/main/java/org/apache/hc/client5/http/impl/cache/RequestViaCache.java