[stable/fluent-bit] add extraLuaScripts config and inject lua script to dedot kube- labels and annotations

[kruftik]

What this PR does / why we need it:

Fixes fluent/fluent-bit#1134. Injects lua function from fluent/fluent-bit#1134 (comment) to fluent-bit containers and use it to replace dots in the keys of kubernetes labels and annotations with underscore to fix data type-related conflicts

Special notes for your reviewer:

Checklist

[Place an '[x]' (no spaces) in all applicable fields. Please remove unrelated fields.]

• DCO signed
• Chart Version bumped
• Variables are documented in the README.md
• Title of the PR starts with chart name (e.g. [stable/mychartname])

[k8s-ci-robot]

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[kruftik]

/assign @hectorj2f

[andreykaipov]

Since this is removing slashes too, I don't think filter.enableDedotKeys as the value name is appropriate, but filter.enableDedotAndDeslashKeys feels too verbose and specific.

Maybe we could abstract this functionality into a generic filter.kubeRemapMetaKeys value so the Lua code here would look as follows:

{{- with .Values.filter.kubeRemapMetaKeys }}
local remapped = string.gsub(k, {{ .pattern | quote }}, {{ .replacement | quote }})
{{- end }}

Now a user can specify exactly how they'd like to remap K8s labels and annotations. The documentation would have to clarify the pattern has to be a valid Lua pattern as per https://www.lua.org/pil/20.2.html though, but for the most part regex is okay too.

Removing both slashes and dots as a chart consumer would then look like:

filter.kubeRemapMetaKeys:
  pattern: '[/.]'
  replacement: ''

[kruftik]

sounds reasonable. now the proposed implementation is used. in addition, made kubeRemapMetaKeys as a list to allow multiple different remappings.

[andreykaipov]

This new value is missing in the README.

Disregarding that though, how would one use this value? I guess what's the benefit over just using extraVolumeMounts?

[kruftik]

fixed.

imo, the extraLuaScripts value is a quite simple way to inject additional Lua scripts to the container while existing extraVolumeMounts is not. the main "problem" here is the need to place the scripts content by some way into the volume where extraLuaScripts is a simple plain-text setting.

[stale]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs. Any further update will cause the issue/pull request to no longer be considered stale. Thank you for your contributions.

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[kruftik]

/assign @hectorj2f

[stale]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs. Any further update will cause the issue/pull request to no longer be considered stale. Thank you for your contributions.

[stale]

This issue is being automatically closed due to inactivity.