feat(translator): Generate KongConfigurationTranslationFailed event when algorithm=sticky-sessions and kong version < 3.11

[randmonkey]

What this PR does / why we need it:

When KongUpstreamPolicy set algorithm to sticky-sessions and Kong gateway version < 3.11, generate a KongConfigurationTranslationFailed event for services using the KongUpstreamPolicy and do not override translated upstream by KongUpstreamPolicy.

Which issue this PR fixes:

closes #7537

Special notes for your reviewer:

Generation of event for Kong Gateway < 3.11.0 is covered by dedicated envtest TestStickySessionsNotSupportedEventGeneration. Big general envtest TestConfigErrorEventGenerationInMemoryMode to pass has to detect this event too, because 3.11.0 is not released yet, so there is no support. But 3.11.0 is around the corner, so when it is updated, this test will fail, and someone needs to adjust it as described in the TODO to cover the situation of not generating this event. There is rather no point in introducing some machinery for testing it now. Proper behavior has been tested manually with the release candidate of 3.11.0, so the update will go smoothly

PR Readiness Checklist:

Complete these before marking the PR as ready to review:

• the CHANGELOG.md release notes have been updated to reflect any significant (and particularly user-facing) changes introduced by this PR

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 77.4%. Comparing base (4ee641e) to head (b6d72d6).

Additional details and impacted files

@@           Coverage Diff           @@
##            main   #7538     +/-   ##
=======================================
- Coverage   77.4%   77.4%   -0.1%     
=======================================
  Files        221     221             
  Lines      25573   25588     +15     
=======================================
+ Hits       19808   19818     +10     
- Misses      4755    4758      +3     
- Partials    1010    1012      +2     

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[tao12345666333]

I believe there are two points that need to be addressed here: in addition to not supporting the sticky-sessions algorithm, it is also necessary to check that setting the stickySessions.cookie and stickySession.cookie_path fields in KongUpstreamPolicy is not allowed.

Of course, for the checks on the last two fields, we might be able to avoid them through a CEL rule.

https://github.com/Kong/kubernetes-configuration/blob/5edaf967a41f5698156813a8a27fa7ecacb9f33e/api/configuration/v1beta1/kongupstreampolicy_types.go#L44-L56

[pmalek]

I believe there are two points that need to be addressed here: in addition to not supporting the sticky-sessions algorithm, it is also necessary to check that setting the stickySessions.cookie and stickySession.cookie_path fields in KongUpstreamPolicy is not allowed.

Of course, for the checks on the last two fields, we might be able to avoid them through a CEL rule.

https://github.com/Kong/kubernetes-configuration/blob/5edaf967a41f5698156813a8a27fa7ecacb9f33e/api/configuration/v1beta1/kongupstreampolicy_types.go#L44-L56

AFAICT we can't use CEL for these because we don't know the Kong version used in the CEL context. We only know it in runtime.

[tao12345666333]

You are right. @pmalek

However, I also submitted a PR to add a CEL rule for it. I will be unavailable for the next few days, so if you think it's valuable, you can merge that PR as well.
Kong/kubernetes-configuration#472