creating bootimages in Fedora for bootc

"bootimage": an image used to start an instance on any given platform. The platform could be very specific (AWS) or generic (i.e. metal).

Today if you want to try out bootc/Image Mode on a particular platform you need to figure out how to start Fedora (or any another linux) on that platform and then take over that instance.

https://docs.fedoraproject.org/en-US/bootc/provisioning-aws/#_no_separate_pre_generated_amis

For people looking to try out image mode I think it would be better if we could just go ahead and create/upload bootimages for the various platforms and then people can try it out directly without really having to follow too many directions.

A second benefit of doing something like this is that we can also use these "vanilla" bootimages to "switch" easily to custom user-built containers (I call this "build your own"). We can even make it really easy to switch non-interactively with some small amount of user-data provided to the instance. Also, hopefully (one day) content already present on the booted node that was common between the booted node and the custom user-built container wouldn't need to be re-pulled

A third benefit of something like this is that if a user is happy with the default experience they don't need to build their own container image at all and can just use the default container we push to the registry for updates of the instance they started.

Since I'm coming from the CoreOS space I see this as something very similar to the bootimages that we have for Fedora CoreOS today (see https://fedoraproject.org/coreos/download?stream=stable), but to attract a wider audience for something like this I don't think we can be as prescriptive as CoreOS has been about initial provisioning. i.e. at a minimum I would think the bootc/Image Mode bootimages would need to support cloud-init.

Thoughts?