Split Ignition support in an Ignition RPM sub-package (like ignition-edge)

[travier]

Describe the enhancement

Ignition support in Fedora CoreOS is now mature and less likely to drastically change. Let's split all the units, config, services, etc. in an ignition RPM sub-package.

This would let us more easily include Ignition support in Project Sagano images: https://gitlab.com/CentOS/cloud/sagano

This will also enable us to de-duplicate the effort with https://github.com/fedora-iot/ignition-edge.

To reduce the impact on development speed, we would enable CI in the new repo and add auto-packaging updates with packit for the Fedora package.

System details

N/A

Additional information

Another alternative is to teach rpm-ostree to handle overlays during compose and use that instead of having the logic in COSA.

[travier]

From today's meeting:

  * AGREED: We'll split Ignition support config and services from
    fedora-coreos-config into another repo and include them in FCOS via
    an Ignition subpackage, similarly to how ignition-edge does it
    today, eventually replacing it  (travier, 17:22:01)

I'll make a PoC before moving forward.

[runcom]

I'll make a PoC before moving forward.

cc @7flying too - I think we could work together on making sure the new package passes CI and it's integrated into edge too

[7flying]

@travier I have some free cycles, so feel free to ping me if you need any assistance, testing etc

[travier]

Current plans:

• Split this into a proper package instead of using a subpackage
• Integrate with Packit to auto-release updates in Fedora
• Integrate with CoreOS CI

[travier]

Great explanation from Benjamin in #1311 (comment)