This brings support for multiple backups pointing to the same borg
server, different repositories, from the same client. We support this by
parsing the SSH authorized key file first and appending allowed
repositories to allow independent definitions of the borg targets.
So that the decryption_keys do not clash we include the repository name
as well as the host in the key. This will lead to new keys being created
for existing hosts in the new format.
Old Format: {{ combine({inventory_hostname: borg_keys.stdout}) }}
New Format: {{ combine({(inventory_hostname ~ '_' ~ borg_repo_name): borg_keys.stdout}) }}
If upgrading from an older version that used just the hostname as the
key, your existing `decryption_keys.yml` can be manually removed once
the new format is also added.