enki should be able to convert an image to Kairos

[jimmykarily]

Part of: #1546

When the user specified a Dockefile or a base (non-Kairos) image, the image has to be converted to Kairos the same way we do using Earthly in our release pipelines.

This conversion from vanilla OS to Kairos has a well defined logic but it's currently implemented in Earthly. We will implement it in enki instead so that we can use Auroraboot to convert vanilla images to Kairos.

Eventually, we should be able to replace the Earthly targets in our pipelines with calls to auroraboot.

[jimmykarily]

We had a discussion and this is what the process should look like:

• We take the user's Dockerfile or image
• We create a multi-stage Dockerfile that combines the user's Dockerfile/image with one from us
• In "our" part of the dockerfile, we copy over all the overlay files and binaries from the framework image
• We also generate the initramfs
• [TBD] Generate an /etc/os-release file (what info should this file include?)
• Build the multi-stage dockefile with kaniko
• Generate additional artifacts from the image (iso, etc)
• Done

To make this happen, we need to have one single framework image for all flavors/models/etc. and blindly copy
all overlay files in place. The scripts themselves should have all the logic on whether they should have any effect or not. E.g. Instead of checking in the dockerfile/earthlyfile whether to copy an overlay file, the overlay file should decide whether to do something or not, by checking if it's running on that specific model/flavor. It should use the kairos-agent to infer the needed information (e.g. like we do here)

[jimmykarily]

Created a story for the work on the overlay files: #1726

[jimmykarily]

WIP here: kairos-io/osbuilder#96