[Security] 9.0.4 release notes

[natasha-moore-elastic]

Resolves #1926: adds the 9.0.4 Security and Elastic Defend release notes.

Preview: Elastic Security

[github-actions]

🔍 Preview links for changed docs

• release-notes/elastic-security/index.md
• release-notes/elastic-security/known-issues.md

[natasha-moore-elastic]

Hey @banderror, this PR just re-adds the same release notes that were originally added in #2080 (which you reviewed), but had to be removed temporarily due to the release being delayed. Sorry for any confusion!

[banderror]

@natasha-moore-elastic Got it, no worries!

I just noticed that for some reason we're missing elastic/kibana#227859 in the 9.0.4 release notes, but it is included in 9.1.0.

On the other hand, elastic/kibana#224676 was documented in the 9.0.4 notes but not included in the 9.1.0 notes.

I'm a bit confused about this and not sure if there's an error to fix here or it is expected.

[banderror]

The elastic/kibana#227803 PR is also release-noted in #2149 but not included in the 9.0.4 notes.

[natasha-moore-elastic]

@banderror I see, thanks for flagging – I'll get this updated! I think some of them might have slipped through if the version labels were added just after I generated the RNs.

Generally, we release-note PRs only for the earliest major version they apply to, so any PRs that have both v9.0.4 and v9.1.0 should only appear in the 9.0.4 RNs.

[banderror]

@natasha-moore-elastic Got it, yep that was my understanding as well. TY!