This commit changes the config format of repositories to the
soon-be-expected `{ "path": "repository-path", }`. The Home Manager
configuration allows a simple string (which will get translated), the
new format by directly using the path attribute, and the one with the
optional label attribute. More information about the background can be
found here https://torsion.org/borgmatic/docs/reference/configuration/
The configuration file format of borgmatic has changed in version
1.8.0:
https://projects.torsion.org/borgmatic-collective/borgmatic/src/branch/main/NEWS
This commit makes Home Manager generate borgmatic's configuration file
using the new format.
Even though the NEWS file indicates that old configuration files are
compatible, this is not 100% the case: empty sections work fine in old
borgmatic but stop working in new ones. I've reported the bug upstream
by email as I couldn't create an account on the forge.
