Add option to not override nginx user

[giladd123]

In nginx, the user directive can only be used when the process is started with the root user, which creates issues when trying to run the proxy in a non-root environment.

The changes presented add the option to not set the directive, while preserving the default behavior of it being included.

[BorisPolonsky]

Declaring user nginx; alone in nginx.conf won't suffice for non-root nginx setup as the ownership related directories (e.g. /etc/nginx, /var/cache/nginx/) would need further adjustment. It would be better to automatically determine from security context.
We'll consider a self-sufficient solution for non-root setups of nginx, taking account this issue, #361 and further adjustments if required as well.

[giladd123]

You're right, removing the declaration alone won't suffice, but if we include #360 we can mount two emptyDir volumes in /var/cache/nginx and /var/run, which does work as a workaround (nginx only needs read permissions on /etc/nginx).

I can work on a more comprehensive solution, but please keep in mind that the 3 PRs I've created do solve the issue while not changing expected behavior.

[BorisPolonsky]

Declaring user nginx; alone in nginx.conf won't suffice for non-root nginx setup as the ownership related directories (e.g. /etc/nginx, /var/cache/nginx/) would need further adjustment. It would be better to automatically determine from security context. We'll consider a self-sufficient solution for non-root setups of nginx, taking account this issue, #361 and further adjustments if required as well.

Closing this issue as we've integrated this option in #363. Note that we still need #361 and #360 for the whole solution.