Generate certificates at runtime for runner test

[joanlopez]

What?

It modifies the TestVUIntegrationClientCerts test on runner_test.go in order to generate certificates at runtime, instead of using pre-generated ones.

Why?

This test is currently failing when runtime.GOOS == "darwin", because it expects the "certificate signed by unknown authority" error but it gets "certificate is not standards compliant" instead, because the pre-generated certificate has a validity of 1000 years since 2022, and that's not considered standards compliant by Apple.

So, instead of having a pre-generated certificate that expires every year (so we'd need to update it every year), this makes the test to generate the required certificates at runtime (so always up to date), which also seems to be fine for MacOS.

Checklist

• I have performed a self-review of my code.
• I have added tests for my changes.
• I have run linter locally (make lint) and all checks pass.
• I have run tests locally (make tests) and all tests pass.
• I have commented on my code, particularly in hard-to-understand areas.

Related PR(s)/Issue(s)

I think it fixes #2578, cause with this I no longer see errors on MacOS.

[joanlopez]

Beyond the new logic to have support for CA cert & key (if parent == nil { ... }), this is the only line from the original method that I have modified (removed), because with this line the test doesn't work (because the generated cert cannot be used to sign later) and without it everything works as expected, so 👌🏻

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (65b2f27) 72.55% compared to head (3d01523) 72.50%.

❗ Current head 3d01523 differs from pull request most recent head d8427ae. Consider uploading reports for the commit d8427ae to get more accurate results

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #3527      +/-   ##
==========================================
- Coverage   72.55%   72.50%   -0.05%     
==========================================
  Files         276      274       -2     
  Lines       20840    20835       -5     
==========================================
- Hits        15120    15107      -13     
- Misses       4758     4762       +4     
- Partials      962      966       +4     

Flag	Coverage Δ
ubuntu	72.50% <ø> (ø)
windows	?

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