This allows the VM to provide a `configuration.nix` file to the VM.
The test doesn't work in sandbox because it needs Internet (however it
works interactively).
The Openstack metadata service exposes the EC2 API. We use the
existing `ec2.nix` module to configure the hostname and ssh keys of an
Openstack Instance.
A test checks the ssh server is well configured.
This is mainly to reduce the size of the image (700MB). Also,
declarative features provided by cloud-init are not really useful
since we would prefer to use our `configuration.nix` file instead.
There are currently two ways to build Openstack image. This just picks
best of both, to keep only one!
- Image is resizable
- Cloudinit is enable
- Password authentication is disable by default
- Use the same layer than other image builders (ec2, gce...)
