Drop Foreman < 3.8 versions support

[archanaserver]

#1826

[ekohl]

I think this current PR should be summarized as "Update forklift_versions role tests to use current versions" or similar.

But taking a step back, I'd combine this with another change: drop older boxes. We have versions.yaml and we can drop older versions there.

What we at least need to keep is currently supported versions (3.10, 3.11 & nightly) and what's needed to release them. To release 3.10, we need n-2 so 3.8. That means you can drop 3.7 and older.

To do that, you need to update the tests, but that's usually not the objective. So the PR summary should then be something like "Drop Foreman < 3.8 versions".

When dropping older version support, you can take a look if there are some version specific hacks that can also be dropped, but there is some downstream concern. Forklift is also used in Satellite so you may need to keep 3.5 support for now.

You can consider dropping the versions 1 by 1, each in a separate commit. Start with the oldest and work your way to the newest.

[archanaserver]

When dropping older version support, you can take a look if there are some version specific hacks that can also be dropped, but there is some downstream concern. Forklift is also used in Satellite so you may need to keep 3.5 support for now.

@ekohl I've been using this file to check the versions compatibility but how can I review the dependency for candlepin, pulpcore and puppet for the selected foreman and katello version?

[ekohl]

Was dropping centos 7 & 8 intended to be part of this PR?

[evgeni]

I thought it's fine as a cleanup? :)

[ekohl]

I'd have preferred it to be more explicit and at least as a separate commit.