Previously, `X-Forwarded-Proto` did not need to be set, and failure to
set `loadbalancer.ips` would merely result in bad IP-address
rate-limiting and incorrect access logs; after 0935d388f0, however,
failure to do either of those, if Zulip is deployed with `http_only`,
will lead to infinite redirect loops after login. These are
accompanied by a misleading error, from Tornado, of:
Forbidden (Origin checking failed - https://zulip.example.com does not match any trusted origins.): /json/events
This is most common with Docker deployments, where deployments use
another docker container, such as nginx or Traefik, to do SSL
termination. See zulip/docker-zulip#403.
Update the documentation to reinforce that `loadbalancer.ips` also
controls trust of `X-Forwarded-Proto`, and that failure to set it will
cause the application to not function correctly.
d46279c41e