make ASO adopt previously managed resources

[nojnhuh]

What type of PR is this?
/kind feature

What this PR does / why we need it:

The goal of this PR is to smooth the transition from non-ASO-backed CAPZ to ASO-backed CAPZ by automatically adopting pre-existing Azure resources that are identified to have been managed by a previous version of CAPZ.

Depending on the resource type, the indicator that it was managed by a previous version of CAPZ will either be the sigs.k8s.io_cluster-api-provider-azure_cluster_* tag on the resource in Azure or a static true for resources not eligible for BYO currently, like managedclusters:

cluster-api-provider-azure/azure/services/managedclusters/managedclusters.go

Lines 125 to 128 in 8e1c9ae

	// IsManaged returns always returns true as CAPZ does not support BYO managed cluster.
	func (s *Service) IsManaged(ctx context.Context) (bool, error) {
	return true, nil
	}

More context in the proposal: https://github.com/kubernetes-sigs/cluster-api-provider-azure/blob/8e1c9aead5a0c7aa7da343331c82c00364a9b9fd/docs/proposals/20230123-azure-service-operator.md#upgrade-strategy

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 #3521

Special notes for your reviewer:

This branch includes this change and the necessary plumbing to make this functional if you'd like to test this yourself: main...nojnhuh:cluster-api-provider-azure:aso-wired

• cherry-pick candidate

TODOs:

• squashed commits
• includes documentation
• adds unit tests

Release note:

NONE

[nojnhuh]

This is ready for review, but I'd like to do some manual smoke testing since these changes aren't exercised by CI yet.

/hold

[codecov]

Codecov Report

Patch coverage: 100.00% and project coverage change: +0.01 🎉

Comparison is base (8e1c9ae) 53.88% compared to head (562f646) 53.90%.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #3662      +/-   ##
==========================================
+ Coverage   53.88%   53.90%   +0.01%     
==========================================
  Files         185      185              
  Lines       18618    18626       +8     
==========================================
+ Hits        10032    10040       +8     
  Misses       8046     8046              
  Partials      540      540              

Impacted Files	Coverage Δ
azure/services/aso/aso.go	93.95% <100.00%> (+0.06%)	⬆️
azure/services/asogroups/spec.go	100.00% <100.00%> (ø)

☔ View full report in Codecov by Sentry.
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[nojnhuh]

This is ready for review, but I'd like to do some manual smoke testing since these changes aren't exercised by CI yet.

/hold

Looking good!

/hold cancel
/retest

[adriananeci]

/lgtm
Maybe not directly related to changes from this PR, but why naming the service asogroups instead of asoresourcegroups? Just to keep it in sync with the groups service or because the name would have been too long? IMO asoresourcegroups sounds less confusing compared to asogroups

[k8s-ci-robot]

@adriananeci: changing LGTM is restricted to collaborators

In response to this:

/lgtm
Maybe not directly related to changes from this PR, but why naming the service asogroups instead of asoresourcegroups? Just to keep it in sync with the groups service or because the name would have been too long? IMO asoresourcegroups sounds less confusing compared to asogroups

Instructions for interacting with me using PR comments are available here. If you have questions or suggestions related to my behavior, please file an issue against the kubernetes/test-infra repository.

[nojnhuh]

/lgtm Maybe not directly related to changes from this PR, but why naming the service asogroups instead of asoresourcegroups? Just to keep it in sync with the groups service or because the name would have been too long? IMO asoresourcegroups sounds less confusing compared to asogroups

There is a little more context here around the package name: #3574 (comment)

Overall, the plan for the other packages under /azure/services is to re-implement them in-place to use ASO so we won't necessarily need to change the package name to distinguish it as "the ASO one." The resource groups package is a little special because the ASO flavor isn't complete yet, so the existing groups package is the only one in use while we iterate on the ASO framework and ASO groups implementations in parallel. Part of #3527 will be to remove the SDK-backed resource groups implementation.

And in general, I'm not 100% sure all the other /azure/services/* packages will deal with exactly one ASO resource like this one does, so I wonder if naming packages aso<aso resource> might not always work out nicely.

[nojnhuh]

/assign @Jont828

[mboersma]

/lgtm

Nice work!

[k8s-ci-robot]

LGTM label has been added.

Git tree hash: 03fa33634824db8f5b96519ef41565b60d53f183

[CecileRobertMichon]

/lgtm
/approve

[k8s-ci-robot]

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