When developing Dokku, it is useful to use a real domain to test actual functionality. This is impossible if the domain is hardcoded to dokku.me in testing.
RHEL blocks users from executing crontab as themselves Because Of Reasons so we need to use sudo instead.
Also refactors file writing to properly support writing the permissions on sudoers files going forward.
Closes#5020
This allows alternative plugins - such as dokku-letsencrypt - to inject scheduled cron tasks into the cron system used by Dokku. Cron systems can choose to include or not include a cron task based on the specified scheduler, and can also optionally use a third parameter to store arbitrary information.
This functionality enables users to manage a global crontab for the Dokku user that contains all scheduled tasks across all apps. Alternative schedulers can implement cron tasks as desired.
