[NopeCharon]

Summary

FluentdSpec has supported user-defined sidecarContainers since 4.5, but the Fluent Bit DaemonSet only ever ran the containers the operator manages itself (fluent-bit, the optional config-reloader and the optional buffer metrics sidecar). Fluent Bit already supports extra volumes and other pod tweaks, but there was no way to run a helper container next to each collector. The issue's example is a liveness sidecar that restarts a fluent-bit that has stopped shipping logs.

This adds sidecarContainers to FluentbitSpec, mirroring the field on FluentdSpec. The containers are appended to the DaemonSet pod template after the operator-managed containers. FluentbitAgent and the legacy inline logging.spec.fluentbit share FluentbitSpec, so the field works in both places.

apiVersion: logging.banzaicloud.io/v1beta1
kind: FluentbitAgent
metadata:
  name: example
spec:
  sidecarContainers:
    - name: fluentbitsidecar
      image: alpine
      command: ["sleep", "infinity"]

Deepcopy, CRDs (config and chart) and the API docs are regenerated. A sample manifest, config/samples/fluentbit_sidecars.yaml, is added and linked from the field documentation.

Test plan

• New TestDaemonSetSidecarContainers in pkg/resources/fluentbit covers no sidecars, sidecars only, and sidecars together with the config-reloader and buffer metrics sidecar, where the user sidecars must come last. It fails without the change.
• On an envtest API server with the generated CRDs, created a Logging and a FluentbitAgent with sidecarContainers and ran the real reconciler. The field survived CRD schema pruning, and the generated DaemonSet had the containers [fluent-bit probe].
• make lint (all three modules) and the pkg/sdk/logging and pkg/resources/fluentbit tests pass.
• Re-running make codegen fmt manifests docs produces no further diff.

Fixes #2333

[promptless-for-oss]

Promptless documentation updates

• Document sidecarContainers for Fluent Bit adds a "Sidecar containers" section with an example to the Fluent Bit guide, and a What's new entry. Docs PR