Tasks: need a way to be notified when as task fails that is external to the tasks system

Right now, the only way to know if a task fails is to write a custom task to see when it fails. An example can be found here: https://github.com/influxdata/community-templates/blob/master/downsampling/monitoring_task.yml#L1

But of course, if the entire tasks system is down, this task won't be run either.

As a user, i would like a way to be notified when a task fails to run that is completely independent from tasks.

Start with the issue description and the linked monitoring_task.yml example. Review how task failures are currently detected and identify what “completely independent from tasks” would require. The issue does not name implementation files, tests, or a specific completion path, so the notification design and acceptance criteria need clarification first.

Written by the indexing model from the issue text.