If our chosen backup repo is a local one, each restic container needs to
mount the local path as a volume, otherwise the data is stuck in the
container itself.
Will pass through the hostname to any snapshots set up.
The hostname is _not_ derived from the random docker container string
but instead takes the name of the _host_ on which docker is running
(from ansible facts).
The hostname in combination with the tag should point to the correct
host -> stack which is being backed up.
Global options such as 'timezone' or 'puid' can be set on a host and all
(relevant) roles will inherit them. Will be used for more variables in
the future.
