feat: sidecar init stability, drop k8s < 1.29 support

[Y0sh1dk]

• use native sidecar containers
• dropping support for severely EOL K8s versions (<1.29)

Fixes: #806

[gemini-code-assist]

Summary of Changes

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This pull request refactors the flagd container injection logic within the OpenFeature operator to leverage native Kubernetes sidecar containers, addressing a known issue. This change aligns the operator with modern Kubernetes practices for managing auxiliary containers, improving the lifecycle management of flagd instances. It's important to note that this update introduces a breaking change for older Kubernetes versions (pre-v1.29) that do not support built-in sidecar containers.

Highlights

• Native Kubernetes Sidecar Injection: Updated the flagd container injection mechanism to utilize native Kubernetes sidecar containers, aligning with modern Kubernetes practices for auxiliary container management.
• Flagd Container Restart Policy: Introduced a RestartPolicy of Always for the injected flagd sidecar container to ensure continuous operation.
• Injection Logic Refinement: Modified the addFlagdContainer logic to target PodSpec.InitContainers instead of PodSpec.Containers for flagd injection.
• Breaking Change Notification: Noted that this change is breaking for Kubernetes clusters older than v1.29, as they do not support built-in sidecar containers.

Changelog

• internal/common/flagdinjector/flagdinjector.go
  • Imported k8s.io/utils/ptr for pointer utilities.
  • Added RestartPolicy: ptr.To(corev1.ContainerRestartPolicyAlways) to the generated flagd container.
  • Modified addFlagdContainer to append and update spec.InitContainers instead of spec.Containers.
• internal/common/flagdinjector/flagdinjector_test.go
  • Imported corev1 and k8s.io/utils/ptr.
  • Removed several blank lines for cleaner code.
  • Updated calls to generatePod to include a new initContainers parameter, passing nil where appropriate.
  • Modified assertions to check expectedPod.Spec.InitContainers[0] instead of expectedPod.Spec.Containers[1].
  • Updated the generatePod function signature and implementation to accept and utilize an initContainers slice.
  • Adjusted getExpectedPod to define the flagd container within InitContainers instead of Containers, and added the RestartPolicy.

Activity

• No human activity (comments, reviews, etc.) has been recorded on this pull request yet.

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[gemini-code-assist]

Code Review

This pull request updates the flagd container injection to use native Kubernetes sidecar containers, which is a great improvement for clusters that support this feature (v1.29+). The changes correctly modify the injection logic to place the flagd container into initContainers with restartPolicy: Always. The tests have been updated accordingly to validate the new behavior. The implementation is solid. I've left one minor comment regarding import consistency in a test file.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 68.72%. Comparing base (499661e) to head (f6b64a9).
⚠️ Report is 95 commits behind head on main.

Additional details and impacted files

@@             Coverage Diff             @@
##             main     #807       +/-   ##
===========================================
- Coverage   86.51%   68.72%   -17.79%     
===========================================
  Files          19       30       +11     
  Lines        1587     2392      +805     
===========================================
+ Hits         1373     1644      +271     
- Misses        173      695      +522     
- Partials       41       53       +12     

Files with missing lines	Coverage Δ
internal/common/flagdinjector/flagdinjector.go	87.71% <100.00%> (ø)

... and 11 files with indirect coverage changes

Flag	Coverage Δ
unit-tests	68.72% <100.00%> (∅)

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[toddbaert]

@Y0sh1dk I've only removed k8s 1.28 and older - the rest work fine as mentioned here: #807 (comment)

I will merge tomorrow unless you object. Thanks a lot. I think maybe some of the tests are redundant, but you can decide.

(I also updated the title/description a bit since it will go into the release notes.)

[Y0sh1dk]

I will merge tomorrow unless you object. Thanks a lot. I think maybe some of the tests are redundant, but you can decide.

@toddbaert Thanks for the updates, have removed the redundant tests and happy for this to go in.