🌱 Add --additional-sync-machine-labels to allow syncing additional labels to Nodes

[ykakarap]

What this PR does / why we need it:

Add an flag to the CAPI manager to dictate the labels that should be synced form the Machine to the node. If the flag is not specified it defaults to:

Has node-role.kubernetes.io as prefix.
Belongs to node-restriction.kubernetes.io domain.
Belongs to node.cluster.x-k8s.io domain.

Any value specified by the flag would be additional to the list to default values.

Which issue(s) this PR fixes (optional, in fixes #<issue number>(, fixes #<issue_number>, ...) format, will close the issue(s) when PR gets merged):
Fixes #11657

/area machine

[enxebre]

Thanks! let's please make sure to add a counter part issue and update the original proposal https://github.com/kubernetes-sigs/cluster-api/blob/12cd150d55330e04b2639396469786a6020a5b82/docs/proposals/20220927-label-sync-between-machine-and-nodes.md

[ykakarap]

TODO:

• Update CAPI Book
• Update the proposal
• Create issue

[nrb]

Thanks for this!

Something that would be useful here is some sort of wildcard support, in case administrators would like all labels propagated.

[vincepri]

Something that would be useful here is some sort of wildcard support, in case administrators would like all labels propagated.

This is supported by setting *

https://github.com/kubernetes-sigs/cluster-api/pull/11650/files#diff-d4d6212206abc46c562f8e0ede7e3c6aa9b87390648a7f25ad96699446b1c525R761-R766

[nrb]

@enxebre An issue was created, #11657.

This PR looks good to me; the documentation is clear, and the use of file path globbing would support my intended use case.

[sbueringer]

Just a few minor findings

[k8s-ci-robot]

@ykakarap: The following test failed, say /retest to rerun all failed tests or /retest-required to rerun all mandatory failed tests:

Test name	Commit	Details	Required	Rerun command
pull-cluster-api-apidiff-main	5f8e673	link	false	/test pull-cluster-api-apidiff-main

Full PR test history. Your PR dashboard. Please help us cut down on flakes by linking to an open issue when you hit one in your PR.

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[sbueringer]

Thx!

/lgtm

/assign @enxebre @nrb @vincepri @fabriziopandini @chrischdi

[k8s-ci-robot]

LGTM label has been added.

Git tree hash: e8198decdcb51738cdbd4d38b3c9eeb9b0f99f4a

[sbueringer]

/test pull-cluster-api-e2e-main

[enxebre]

/lgtm

[vincepri]

/approve

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: vincepri

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[ykakarap]

/cherry-pick release-1.9

[k8s-infra-cherrypick-robot]

@ykakarap: #11650 failed to apply on top of branch "release-1.9":

Applying: sync machine labels
.git/rebase-apply/patch:74: trailing whitespace.
A default list of labels would always be synced from the Machines to the Nodes. An additional list of labels can be synced from the Machine to the Node by providing a list of regexes as a flag to the manager. 
.git/rebase-apply/patch:84: trailing whitespace.
- [ ] 01/09/2025: Update to support configurable label syncing Ref:[11657](https://github.com/kubernetes-sigs/cluster-api/issues/11657) 
warning: 2 lines add whitespace errors.
Using index info to reconstruct a base tree...
M	controllers/alias.go
M	internal/controllers/machine/machine_controller.go
M	main.go
Falling back to patching base and 3-way merge...
Auto-merging main.go
CONFLICT (content): Merge conflict in main.go
Auto-merging internal/controllers/machine/machine_controller.go
Auto-merging controllers/alias.go
error: Failed to merge in the changes.
hint: Use 'git am --show-current-patch=diff' to see the failed patch
hint: When you have resolved this problem, run "git am --continue".
hint: If you prefer to skip this patch, run "git am --skip" instead.
hint: To restore the original branch and stop patching, run "git am --abort".
hint: Disable this message with "git config advice.mergeConflict false"
Patch failed at 0001 sync machine labels

In response to this:

/cherry-pick release-1.9

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