Documentation: Gunicorn deployment should probably mention the usage of a proxy

[Klaas van Schelven]

The current ​documentation for deploying using gunicorn(which happens to be the top entry in the list of deployment options) does not mention using gunicorn should probably be installed behind a proxy, even though this is the very first thing the ​gunicorn deployment documentation itself says. Since not putting a proxy in front is insecure, this is probably good advice to add.

Given that various specific settings are required (#35450) when setting up a proxy, it would be nice to refer those from the same page.

[Sarah Boyce]

Happy to review improvements here 👍

[Sarah Boyce]

Please either link the PR or make sure the PR title has the prefix "Fixed #35451 --" so that it will be linked automatically when you set "Has patch" to "Yes"

[Sarah Boyce]

To reduce the maintenance burden, the Django docs avoid stating duplicate information that is available in official linked docs/sources and is not Django specific.
As the advice of deploying gunicorn behind a proxy is the very first thing it says, this also means this is not difficult to find. Hence there is little value in having this repeated in the Django how to.