Container volume backup logic has been moved to a (largely equivalent)
external script, allowing for future expansion of functionality. In
addition, a `rclone-pull@` service has been added and set up as a default
dependency for the `container-volume-restore@` service, allowing for
automatic set up of servers based on latest remote backups.
Symbolic links are now synchronized verbatim (i.e. the links themselves,
not their destinations) to allow for restoring our pattern of linking to
the latest backup file.
In addition, the destination remote and path can now be configured
individually in drop-in files, but still default to the encrypted
remote.
This commit adds a new systemd service, `rclone-sync@.service`,
templated against the absolute path of a directory to keep in sync with
a (presumably) remote store.
Support for Backblaze B2 endpoints has been set up by default, but the
specific remote type can be configured via the `RCLONE_REMOTE_TYPE` host
variable. In addition, a default-passthrough remote that encrypts data
against a static password and salt has been defined under the `crypt`
name, and can also be used as the `RCLONE_DEST` of choice.
