Add support for trusting X-Forwarded-For header to get client IP

[Skyler84]

This fixes #882
falls back to remote ip if header unavailable

Added trust_x_forwarded_headers option in warpgate.yaml config

http:
  enable: true
  listen: "0.0.0.0:8888"
  certificate: "./data/tls.certificate.pem"
  key: "./data/tls.key.pem"
  trust_x_forwarded_headers: false

[Eugeny]

Thanks! Would you consider adding support for X-Forwarded-Proto in the same PR to cover both bases?

[Skyler84]

Sure thing, what do you think the X-Forward-Proto should affect. I noticed that there should be support for x-forwarded-... already but it's all lowercase, but i'm not sure how well this will work as some proxies use X-Forwarded-... with upper case words etc

[Eugeny]

It's used to construct external URLs for SSO and SSH 2FA. The case doesn't matter because header name matching in both http and poetry is case insensitive.

[Skyler84]

header name matching in both http and poetry is case insensitive

Ah perfect, I should be able to work on that just fine then. I'll update my bits to use the static header string declarations!

[Skyler84]

This works quite nicely now, have tested running behind traefik with multiple hostnames, ports and http/https and the SSO redirect works perfectly. Tested with SSH SSO as well and appears to be working

[Eugeny]

I've reordered things slightly for readability ✌️

Thanks!