TODO: use different linux user to run qzfr-api and qzfr-web processes & systemd services

[ehanahamed]

We should use a different, non-root, linux user in quizfreely-api's and quizfreely-web's service files (by setting User=, by default User= is root)

This is just a reminder for myself to update quizfreely-api.service, quizfreely-web.service, and related documentation (mostly production setup docs, since developers/contributors don't need service files for development, it's only for production)