Kanboard supports running cron jobs via CLI. There are hosting services
that don't offer CLI access, but they do offer calling a URL
periodically. This feature is often used as a CLI cron job replacement.
This commit adds a CronjobController called by "/cronjob" URL that will
execute cron jobs as they were executed via CLI. The URL has public
access, but is protected using the webhook token. The "/cronjob" URL
should be called via HTTPS.
Miodrag Tokić