Add netbird support

[victoitor]

Netbird is an alternative to Tailscale (issue to include support) which provides essentially the same functionality of creating an overlay network based on wireguard with SSO and MFA. It is also quite popular but, unlike tailscale, both the client and the management server are open source.

It would be nice to be able to configure it through the IncusOS network API to provide a secure wireguard overlay network between the hosts and for remote access.

[victoitor]

I was watching the tailscale video and just heard the comment on not wanting to include every possible solution and, since I opened this issue, I have to say that I totally agree on the comment. Just by hearing that, I wanted to say that, even though I like netbird better, I really don't think it's such a big issue if it's not implemented.

I opened this issue thinking it would definitely not be a priority and mostly as a heads up that this solution exists and is also popular.

[victoitor]

While I'm on this subject of the tailscale video, I was a bit puzzled by the next comment though, when @stgraber mentioned a disk size impact. I thought applications were implemented with mkosi sysext and that they would have absolutely no impact on disk size if it was not installed. Did I understand something incorrectly?

[stgraber]

We've seen enough folks mention Netbird that we're quite likely to add that one still.

Tailscale and Netbird are not added as applications but as services, all of those are built into the IncusOS base image.

[victoitor]

Still something I don't understand. Can't a service be an integration together with an application? The integration would be able to run the service when the application is installed. That way, a service would basically be very little extra image space (just the code for the integration with the installed application). What would be the issue of treating a service like this?

[stgraber]

That can be done, the Ceph service kinda works like that (it's included in the Incus application). If space or quality of some of those services becomes a major concern, we are likely to go with that approach, though maybe more likely to bundle a bunch of them together into one application rather than have dozens of applications to keep track of.