Foreman export scripts for user-level systemd on Ubuntu 16.04+

# Gemfile
gem "foreman-export-systemd_user"

then

bundle exec foreman export systemd-user --app <app-name>

Note that this may break from foreman's protocol a bit, because it starts the processes after export. It does this by running the following:

loginctl enable-linger
systemctl --user enable <app-name>.target
systemctl --user restart <app-name>.target

After forgetting to run these steps enough times, I just decided to bake it into the export.