users module does not allow ssh_import_id and ssh_authorized_keys at the same time

[Niels Robin-Aubertin]

I'm on ubuntu 22.04, using multipass 1.10.1 with a cloud-init file to instanciate a simple server:

```yaml
users:
  - name: ubuntu
    ssh_authorized_keys:
      - ssh-ed25519 AAAAC3NzaC1lZDI1NTE5AAAAIOkF+W1ETkZQr5PWhcugCVh3aSyNDFTYQRRblh7prGXN
    ssh_import_id:
      - lp:nrobinaubertin
```

I launch the instance with:
```shell
multipass launch -n simple_instance -d 10G -m 1G -c 1 --cloud-init cloud-init.yaml 22.04
```

And I check the authkeys file with:
```shell
multipass exec simple_instance -- cat /home/ubuntu/.ssh/authorized_keys
```

The key from `ssh_authorized_keys` is there but not the one from `ssh_import_id`.
From the documentation website and the examples given [here](https://cloudinit.readthedocs.io/en/latest/topics/examples.html) I would expect both keys to be present.

[Alberto Contreras (aciba)]

Thanks, nrobinaubertin, for reporting this.

Could you please attach the instance logs[1]?

[1] https://cloudinit.readthedocs.io/en/latest/topics/bugs.html#collect-logs

[Niels Robin-Aubertin (nrobinaubertin)]

Here is the log of an instance (created as written in the first message)

[Alberto Contreras (aciba)]

Thanks, nrobinaubertin. I have reproduced this behavior on multipass and lxd.

[James Falcon (falcojr)]

Tracked in Github Issues as https://github.com/canonical/cloud-init/issues/4045