Rethink UpgradableVersions

[slonka]

What happened?

Here https://github.com/kumahq/kuma/pull/10574/files I modified upgradeable versions so that during stabilisation it passes. There were multiple ideas on how it should look like (@lahabana @michaelbeaumont @jakubdyszkiewicz). Please fill in the issue from slack chat.

From the chat:

so you'd want:
master --> 2.8-preview, 2.7-preview
release-2.8 --> 2.7-preview, 2.6-preview
release-2.7 --> 2.6-preview, 2.5-preview

i think personally it's enough just to use preview only if there isn't a release yet.
we can always do preview, but it does introduce a sort of assumption that the preview build for a branch will definitely be released before master
this is almost guaranteed when there's no version released, i.e. what we have now, because it means that branch is the next minor release. there's no way for a user to get a version of 2.8 that has a stability guarantee yet.
but in general, say you have 2.7.0 and 2.8.0, you could make a change on 2.7 preview, so that 2.8 passes the upgrade test, so you release 2.8.1 or whatever, but if you haven't actually released 2.7 preview -> 2.7.1 then the upgrade might fail 

Ok so looking at it these tests use helm charts so you're kind of gutted if you don't have an actual full release

another angle is how to get the preview image information to the test?

[slonka]

Triage: let's gather more data on what's the perfect solution and then think about what we can implement

[github-actions[bot]]

This issue was inactive for 90 days. It will be reviewed in the next triage meeting and might be closed. If you think this issue is still relevant, please comment on it or attend the next triage meeting.