[FEATURE] notify all maintainers when Nightly build fails

[mgovers]

Describe the feature request

Currently, the Nightly build only notifies a single person if it fails, cfr. the documentation in https://docs.github.com/en/actions/monitoring-and-troubleshooting-workflows/monitoring-workflows/notifications-for-workflow-runs

This means, that if the person who last edited the schedule of the Nightly build is on holiday, but the Nightly build fails, then none of the other maintainers will be notified.

We will want to notify all maintainers or people registered to notifications on the repo.

NOTE: also PGM-IO needs to be updated

TBD

how do we want to design this? e.g.

• [ ] opt-in using user repo notification settings
• [ ] all people in maintainers.md
• [ ] opt-out
• [ ] manually in the pipeline