feat: added external_proxy_header option

[hdhog]

#885 added new options external_proxy_header

defaults

external_proxy_header:
  host: "host"
  proto: "x-forwarded-proto"

[Eugeny]

Thank you for the PR! Is your plan to use host: x-forwarded-host in your configuration? In this case, do you think it would make more sense to simply add a trust_proxy_headers config option and allow fallback from x-forwarded-host to the normal host so that it works both "internally" and "externally"?

[lanrat]

@Eugeny Is there any chance you could merge this or another fix for the host header behind a reverse proxy?

Currently, Warpgate is broken when behind a reverse proxy due to it always adding its internal listen url to the callback.

[Skyler84]

I've had Warpgate working fine behind a reverse proxy (Traefik), as long as the external_host field is set warpgate redirects correctly!
I do like the suggestion of trust_proxy_headers so that Warpgate would pick up on those if present, otherwise fallback to Host!

[Eugeny]

Closing in favour of #907