#CURLOPT_HTTPHEADERwill be used in requests both to servers and proxies. With this option enabled,
#CURLOPT_PROXYHEADERwill not have any effect.
#CURLOPT_HTTPHEADERheaders only get sent to a server and not to a proxy. Proxy headers must be set with
#CURLOPT_PROXYHEADERto get used. Note that if a non-CONNECT request is sent to a proxy, libcurl will send both server headers and proxy headers. When doing CONNECT, libcurl will send
#CURLOPT_PROXYHEADERheaders only to the proxy and then
#CURLOPT_HTTPHEADERheaders only to the server.