Allow the usage/creation of a User Managed Identity for AKS kubelet identity

[naioja]

**Problem description
AKS supports multiple user managed identities, one of which is the kubelet identity.

• https://learn.microsoft.com/en-us/azure/aks/use-managed-identity#summary-of-managed-identities

A Kubelet identity enables access granted to the existing identity prior to cluster creation. This feature enables scenarios such as connection to ACR with a pre-created managed identity.

In this scenario AKS is going to use the User Managed Identity created prior to cluster setup in order to do ACR operations permitted with that specific identity.

**Solution description
As a user I would like to either be able to provide a User Managed Identity to the cluster setup process with necessary rights on ACR or have one created and assigned for me with the ability to choose the ACR rights to be assigned to the identity.

**Alternatives
As the documentation describes if the cluster is not created with a managed kubelet identity the user cannot assign one :

• https://learn.microsoft.com/en-us/azure/aks/use-managed-identity#limitations-1

[iamvighnesh]

I'd like to work on this one. @Gordonby we might need a discussion on the design part. I will reach out to you separately.

[github-actions]

Issue smells stale, no activity for 30 days. Stale Label will be removed if the issue is updated, otherwise closed in a month.

[github-actions]

Issue smells stale, no activity for 30 days. Stale Label will be removed if the issue is updated, otherwise closed in a month.

[JimPaine]

I'll help pick this up.

Initial thoughts

• Ability to bring your own UAI
• Create UAI if not supplied
• Must meet prereqs i.e. rbac enabled and user assigned identity for control plane
• Work with existing UAI for control plane work
• Handle role assignment requirement between the two identities

@iamvighnesh would you still like to work on this as well?

[deepdolphin]

Documentation for reference: https://learn.microsoft.com/en-us/azure/aks/use-managed-identity#create-a-cluster-using-user-assigned-kubelet-identity