Add support for filtering users based on organizationId - #37975

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.webauthn.AppInitiatedActionWebAuthnTest#cancelSetupWebAuthn

Keycloak CI - WebAuthn IT (chrome)

java.lang.AssertionError: Event expected
	at org.junit.Assert.fail(Assert.java:89)
	at org.junit.Assert.assertTrue(Assert.java:42)
	at org.junit.Assert.assertNotNull(Assert.java:713)
	at org.keycloak.testsuite.AssertEvents.poll(AssertEvents.java:95)
...

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org.keycloak.testsuite.webauthn.AppInitiatedActionWebAuthnTest#proceedSetupWebAuthnLogoutOtherSessionsNotChecked

Keycloak CI - WebAuthn IT (chrome)

java.lang.AssertionError: Event expected
	at org.junit.Assert.fail(Assert.java:89)
	at org.junit.Assert.assertTrue(Assert.java:42)
	at org.junit.Assert.assertNotNull(Assert.java:713)
	at org.keycloak.testsuite.AssertEvents.poll(AssertEvents.java:95)
...

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Thanks for the contribution and for raising this, @msvechla!

I understand the need — the organizations members endpoint currently doesn't offer the same rich filtering
capabilities as the users endpoint, which makes it harder to work with organization members at scale.

That said, I don't think adding organization-aware filters to the users endpoints is the direction we want to go.
We'd prefer to keep organization concerns within the organization API itself, rather than spreading them across
users endpoints.

The right path forward is enhancing the organization endpoints (e.g., GET
/admin/realms/{realm}/organizations/{org-id}/members) with the filtering and search capabilities that are currently
missing. I see that #38090 is already heading in that direction, which is great.