Support for running behind anubis proxy

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Anubis - https://anubis.techaro.lol is a proof of work based proxy to deter bots. Though most of the functionality worked when setting it up, Service Desk was broken. It failed to create any tickets. Once anubis proxy was removed, service desk was creating tickets again. So we have removed anubis for now, but would like to add it back after fixing Service Desk.

Ideally service desk should not be going through the public interface to create tickets. But if even if it was failing, all the mails got removed as processed from inbox even when ticket creation failed. So gitlab should check if tickets are actually created before deleting mails from inbox.

Please suggest how to run service desk behind anubis. As this issue of bots taking down entire gitlab instances, this is relevant to many instances. gitlab.gnome.org already running it live for some time.

Both gitlab and anubis run as services in same docker-compose.yml and use the docker network ip address to communicate (identified by hostname in docker-compose.yml). There is also an haproxy sitting in front of anubis. browsers -> haproxy -> anubis -> nginx -> gitlab/puma

Edited by 🤖 GitLab Bot 🤖