`UX & maintenance`: Transform active run-time components to be image-based or improve them

[fiftydinar]

Objective

This issue will investigate on which components are used in run-time of the Gidro-OS as a script, systemd service or some other form, in order to transform them to be image-based (inside the image).

run-time > image-based

If they can't be transformed, then investigate how to improve those run-time components to be more reliable.

Advantages

This transformation should improve the reliability, ease of maintenance & by that, the UX of Gidro-OS.

List of active run-time components

default-flatpaks BlueBuild module

It is used as a run-time script to manage system & user flatpaks of Gidro-OS.

While installation of flatpaks can be done inside the ISO, that is a 1-time operation only & any updates to flatpaks that can happen in meantime won't be applied.
It also needs to be assured that flatpaks will get installed when image rebase installation method is used, so that's another usecase which this module supports as the active run-time component.

Ideally, this work would be done in flatpak upstream, but that is a slow progress:
flatpak/flatpak#5579

Copying files to $HOME with /usr/etc/skel

While this modification is technically inside the image, the operation is done in run-time only once when users are created.
But if any of the files in /usr/etc/skel are updated inside the image after user creation, that update won't ship to the user, which is not the ideal UX.

Discussion regarding this issue is located here:
blue-build/modules#118