Given that

• Workbench and API server don't run as daemons, per se
• We can't just assume they will run under nginx -- some sites run passenger in Apache instead

..."add systemd files" isn't really relevant.

One way we could ease installation is to create new packages "arvados-workbench-nginx" and "arvados-api-server-nginx" which

• Assume rvm is in use
• Assume nginx is in use
• Install relevant config files in /etc/nginx/sites-available/ (TBD: does this work for non-debian?)
• Don't affect sites that don't use nginx and rvm

See rt4-apache2 and daemontools-run packages for examples of this pattern.