Hetzner-snap-and-rotate

Support the values of server labels in snapshot name templates

Period rotation numbers are now contiguous even if a rotation period does not contain a snapshot.

Reduce overlap of snapshot rotation periods

Removed the support for sliding periods since it could cause unwanted deletions of rotated snapshots due to the jitter of new snapshot instants.

Note that this can happen also with fixed periods if taking a snapshot may finish either shortly before of shortly after a period boundary.

Fix: server not restarted after failed snapshot

Fix: script terminates with error when attempting to shut down a server