✨ Backport KCP Rollout Strategy to v1alpha3 api

[jan-est]

This PR backport KCP Rollout Strategy feature 4073 to v1alpha3 api for next v0.3.x release.

[k8s-ci-robot]

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[neolit123]

what is the CAPI stance on backporting features?
upstream k8s forbids it unless something is completely blocking (or broken), but subprojects can define their own rules.

EDIT: this might be a detail missing in https://github.com/kubernetes-sigs/cluster-api/blob/1c541d922f20b343ff68be459ca489d8d28745b3/VERSIONING.md

[jan-est]

what is the CAPI stance on backporting features?
upstream k8s forbids it unless something is completely blocking (or broken), but subprojects can define their own rules.

EDIT: this might be a detail missing in https://github.com/kubernetes-sigs/cluster-api/blob/1c541d922f20b343ff68be459ca489d8d28745b3/VERSIONING.md

Backporting this feature was agreed on community meeting yesterday. This is not breaking change if I understood right? And my understanding is that backporting in CAPI was relaxed a while ago.

[CecileRobertMichon]

For reference: #3960

https://github.com/vincepri/cluster-api/blob/master/CONTRIBUTING.md#backporting-a-patch

[CecileRobertMichon]

/ok-to-test

[CecileRobertMichon]

/retest

[CecileRobertMichon]

/lgtm
/milestone v0.3.x
/assign @vincepri

[fabriziopandini]

Question: should we wait for back porting the E2E test before merging this change in 0.3, which is our current "production" release?

[CecileRobertMichon]

@vincepri @fabriziopandini this PR is a backport of #4073, aren't we introducing risk by suggesting changes here that weren't in the additional PR? I would prefer if there is anything that needs to be changed and wasn't caught in the initial review of #4073 that a follow up PR be open against main and then both be backported together, that way we stick to clean cherry picks (unless anything is v1alpha3 specific).

[fabriziopandini]

@CecileRobertMichon 100% agreed to strive for a clean cherry pick (and document this in our contributor guidelines)
Unfortunately, given that the differences between the two branches are considerable, this is getting really difficult, but I think that for the changes required in this PR this is doable

[jan-est]

@CecileRobertMichon @vincepri @fabriziopandini just let me know if you want me to do something else for the PR.

[fabriziopandini]

@jan-est let's merge this PR as it is, implement the fix proposed in #4293 (comment) in a new PR on v1alpha4, and then backport.

What is the status of the PR implementing E2E tests for scale in?

[jan-est]

@jan-est let's merge this PR as it is, implement the fix proposed in #4293 (comment) in a new PR on v1alpha4, and then backport.

Ok, I will work on that. @fabriziopandini could you quickly check is the what we are after 4376

What is the status of the PR implementing E2E tests for scale in?

Not any comments so far and tests are passing. 4347

[jan-est]

@jan-est let's merge this PR as it is, implement the fix proposed in #4293 (comment) in a new PR on v1alpha4, and then backport.

@fabriziopandini now when 4376 is merged, should I wait this PR to be merged before backport 4376?

[vincepri]

@jan-est Feel free to include the commit here

[jan-est]

@jan-est Feel free to include the commit here

4376 changes added to this PR.

[fabriziopandini]

/lgtm

[fabriziopandini]

/approve

[k8s-ci-robot]

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