Add support for restore mode

[mgruner]

Zammad 7.0 will feature restoring backups in docker. This happens inside the zammad-backup container, which therefore needs to mount the zammad-storage volume in rw mode rather than ro so that files can actually be restored.

Breaking Change

This change of the mount point must be transferred to any local docker-compose.yml definitions that are already deployed and need to be updated.

[waja]

Is this something that can be done via GUI or is there CLI work needed? If there is operational work required, the write mount can be overridden when a restore is needed. This is a bit more safety but a bit more uncomfortable.

[mgruner]

The admin needs to provide the restorable backups in the restore folder in the zammad-backup volume. This can be done via CLI, but also via Portainer for example by running docker images like filebrowser which provide a browser based UI for managing the volume content.
More changes incoming.

[mgruner]

Is this something that can be done via GUI or is there CLI work needed? If there is operational work required, the write mount can be overridden when a restore is needed. This is a bit more safety but a bit more uncomfortable.

This is right, but it would not work with scenarios like Portainer based deployments, as it requires modification of the yaml file.

[github-actions]

This PR has been automatically marked as stale because it has not had recent activity.
It will be closed if no further activity occurs. Thank you for your contributions.

[mgruner]

TODO: revert before merging