Unreported flaky test detected

If the flaky tests below are affected by the changes, please review and update the changes accordingly. Otherwise, a maintainer should report the flaky tests prior to merging the PR.

org.keycloak.testsuite.model.session.OfflineSessionPersistenceTest#testPersistenceMultipleNodesClientSessionsAtRandomNode

Keycloak CI - Store Model Tests

java.lang.AssertionError: 
Can't retrieve offline session for c6d2ca80-e856-4023-b47f-8af1a563ebc4
Expected: not null
     but: was null
	at org.hamcrest.MatcherAssert.assertThat(MatcherAssert.java:20)
...

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@vmuzikar Thanks, yep I'd say it's a good start for this. However, for the automatic validation based on the annotations, we'd need to do some more things which would not be so easy to do and would require possibly some discussion.

Possible approaches:

1. Execute the validation manually inside the code
2. Having resources (APIs) as a CDI Beans for which the validation is run automatically

I'm inclined more to (2) as it's a recommended way in applications and on Quarkus side and it could simplify a lot of things for us. I'll try to do some prototype on this matter.