return 429 error if ES api key auth returned 429

[juliaElastic]

What is the problem this PR solves?

Misleading 401 unauthorized response when ES API key auth returns 429 error.

How does this PR solve the problem?

Return 429 from Fleet Server API if the root cause is ES auth 429 error.

How to test this PR locally

Tested by running a scale test with a custom image with changes from this pr: https://buildkite.com/elastic/observability-perf/builds/2421#018da31f-8f18-43c5-aac0-5d559f0152cb

Errors show up as 429:

Design Checklist

• I have ensured my design is stateless and will work when multiple fleet-server instances are behind a load balancer.
• I have or intend to scale test my changes, ensuring it will work reliably with 100K+ agents connected.
• I have included fail safe mechanisms to limit the load on fleet-server: rate limiting, circuit breakers, caching, load shedding, etc.

Checklist

• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• I have made corresponding change to the default configuration files
• I have added tests that prove my fix is effective or that my feature works
• I have added an entry in ./changelog/fragments using the changelog tool

Related issues

[jsoriano]

Not tested myself, but change makes sense, thanks!

Would it be possible to add a test for this?

[juliaElastic]

Would it be possible to add a test for this?

I didn't see existing unit tests on this, I'll try to add.

[jsoriano]

Thanks for adding tests 👍

[juliaElastic]

buildkite test this

[juliaElastic]

buildkite, test this

[juliaElastic]

buildkite test this

[michel-laterman]

@juliaElastic, Should we backport this to 8.13?

[elastic-sonarqube]

Quality Gate passed

Kudos, no new issues were introduced!

0 New issues
0 Security Hotspots
92.9% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube