Summary

This is a follow-up PR fixing document, per discussion at #1974 (comment).

ProxyHeadersMiddleware is not making use of X-Forwarded-Port header. X-Forwarded-Port header contains the listening port of the reverse proxy (usually a load balancer). X-Forwarded-Port header does not contain the client's source TCP port, thus should not be used to populate source address.

Checklist

• I understand that this PR may be closed in case there was no previous discussion. (This doesn't apply to typos!)
• I've added a test for each change that was introduced, and I tried as much as possible to make a single atomic change.
• I've updated the documentation accordingly.