Feature: compatibility with reverse proxy headers (X-Real-IP and/or X-Forwarded-For)

[erikmd]

Related user(s):

@erikmd

Related issue(s) or PR(s):

No response

Related project scope(s):

web API

The problem:

• In production environment, learn-ocaml may be combined with a reverse proxy such as nginx or træfik.
• A resulting issue is that the IP seen by learn-ocaml is always the same (that of the local network)

Wanted solution:

It would be good to:

• add a flag-or-env-var replacing the incoming IP by that of X-Real-IP, or:
• add a depth(≥1) flag-or-env-var replacing the incoming IP by the nth last IP in X-Forwarded-For
  (0→X-Real-IP; None→incoming-IP)

Considered alternatives:

No response

Additional context:

See e.g. https://doc.traefik.io/traefik/middlewares/http/ipwhitelist/