TrueNAS Scale - Nextcloud config.php pass forwarded_for_headers as ENV

ENVs like OVERWRITEHOST and OVERWRITECLIURL work like a charm to overwrite config in Nextcloud’s config.php like mentioned here.

How is it possible to do it for forwarded_for_headers?
I would assume it is just FORWARDEDFORHEADERS or FORWARDED_FOR_HEADERS. But how how can I simulate ['HTTP_X_FORWARDED', 'HTTP_FORWARDED_FOR']?

The config.php entry would look like:
'forwarded_for_headers' => ['HTTP_X_FORWARDED', 'HTTP_FORWARDED_FOR'],