[Feature Request] Allow running as non-root user

[elaurensx]

I only publicly expose services which are running as non-root so would appreciate it if this could be the case as well for firefly-pico.

Thanks!

[cioraneanu]

Thanks for opening an issue. This is currently not a high priority, but you can give it a shot and submit a PR.

We already have the user www-data which is used by nginx and php-fpm. Not sure if anything else is missing but there's a chance we only need a USER www-data to the Dockerfile.