Revere proxy

[Thisora]

Hi !
I would like to use grav as a service behind a reverse proxy inside my cluster (kubernetes).
The fact is i have a rewrite-target instruction which let me place my service on a certain URL seamlessly.
For exemple http://exemple.com/grav will automatically send the request to my grav service but at url http://exemple.com/ .
The HTML load correctly but every ressources (like css) are not loading because request url is wrong.
For exemple theme is trying to load http://exemple.com/user/themes/quark... which of course does not exist (should be http://exemple.com/grav/user/themes/quark...).

I tryed with/without parameters reverse_proxy_setup: true and absolute_urls: false in file config/www/user/config/system.yaml but that didn't solve the problem.

In fact i look for a way to use relative url to ressources.
Sorry if i missed something obvious.