[feat] Improve the process of updating Cobbler

[nodeg]

Is your feature request related to a problem?

Both a feature request and something to solve the problem of updating Cobbler.

Provide a detailed description of the proposed feature

When updating Cobbler not only from higher versions but also from minor releases, there are breaking changes which have to be handled.

2.x --> 3.0.0

• use v2 to v3 script

3.0.0 --> 3.0.1

• modules.conf migration (settings-migration-v1-to-v2.sh)

3.1.1 --> 3.1.2

• Hash handling in users.digest file. (#2299)

3.2.0 --> 3.2.1

• new settings.yaml
• int to bool migration

3.2.1 --> 3.3.0

• replace getter/setter with Python properties
• renaming boot_loader to boot_loaders
• renaming gpxe to ipxe
• migration from floats to ints
• Obsolete settings.d directory, we don't want to support this anymore.

other

• Adjust Cobbler completions
• maybe introduce an abstraction layer to map old values to the new ones?

This list is not complete. @SchoolGuy @watologo1 feel free to edit and update this post.

[SchoolGuy]

So the thing that we will do is that we will take V3.2.1 as a baseline and will make an initial migration to V3.3.0 which is a bit special, after that a generic framework we will create will do all future migrations in the settings.yaml file.

[SchoolGuy]

That would mean that even if you skip 100 versions of the settings we will migrate you automatically one by one until you reach the version you want to run.