OVH/Kimsufi are deprecating my current server by the end of the year. So
let's migrate to a new host.
This was more painful than initially planned, OVH introduced a change to
their rescue system which messes with the NixOS installation [1].
In the end I used a kexec image [2] to run the installation.
[1]: https://github.com/NixOS/nix/issues/7790
[2]: https://github.com/nix-community/nixos-images
