Investigate using velero's defaultVolumesToRestic
We currently use the "opt-in" approach to select which pod volumes velero/restic should back up. This has a big disadvantage: when an upstream chart -- we've already experienced this for nextcloud -- changes the supposedly internal pod's volume names, we fail to back up those volumes. Unfortunately, velero only registers this as a warning, not a (partial) failure, so this could even go undetected.
Since a while there is also an "opt-out" approach, using the defaultVolumesToRestic
helm value / --default-volumes-to-restic
setting: velero docs. We'll probably want to switch to that.