Ensure no new AKS LBs are created w/ Basic SKU

[jackfrancis]

What type of PR is this?

/kind cleanup
/kind deprecation

What this PR does / why we need it:

This PR removes the (non-working) LB SKU configuration of "Basic" from the v1beta1 AKS types.

A code audit suggested that the self-managed LB SKU flows already require "Standard", so I think we're O.K. there.

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 #

Special notes for your reviewer:

TODOs:

• squashed commits
• includes documentation
• adds unit tests
• cherry-pick candidate

Release note:

Ensure no new AKS LBs are created w/ Basic SKU

[k8s-ci-robot]

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[jackfrancis]

@nojnhuh I did observe that config/aso/crds.yaml refers to Basic LB SKU as a schema option, does that suggest that an upcoming consumption of a new ASO version will take care of that?

[nojnhuh]

In what way exactly is a basic SKU load balancer "non-working"? Does AKS give an error if that's specified?

@nojnhuh I did observe that config/aso/crds.yaml refers to Basic LB SKU as a schema option, does that suggest that an upcoming consumption of a new ASO version will take care of that?

I see the next AKS API version included in the latest ASO release still lists Basic as a valid value: https://azure.github.io/azure-service-operator/reference/containerservice/v1api20250801/#ContainerServiceNetworkProfile_LoadBalancerSku

I don't see any reason to deviate from what ASO is doing here. @matthchr is ASO doing anything special for that value?

[matthchr]

Does AKS give an error if that's specified?

I think AKS does, but maybe we haven't actually taken this SKU out of the REST API specs? That's probably an oversight on AKS API management side, I'll track it down. Removing Basic is probably correct here though as AFAIK it doesn't work. I've looped you two in on the internal thread I started on this topic as well to get clarity.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 44.55%. Comparing base (23d5dbb) to head (9d9ace1).
⚠️ Report is 40 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #5958   +/-   ##
=======================================
  Coverage   44.54%   44.55%           
=======================================
  Files         279      279           
  Lines       25140    25148    +8     
=======================================
+ Hits        11199    11205    +6     
- Misses      13128    13130    +2     
  Partials      813      813           

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[bryan-cox]

nit: Valid/Invalid SKU over Valid/Invalid Version

[bryan-cox]

Should there be an API comment left to let users know this field was removed/deprecated?

[bryan-cox]

/lgtm

[k8s-ci-robot]

LGTM label has been added.

Git tree hash: 197f5cec643c8d2430949fb9c98621ef78db472e