Add support for aks managed identities

[gshaw-pivotal]

1. What this PR does / why we need it:

Support managed identities specification when creating and updating AKS clusters

2. Which issue(s) this PR fixes

N/A

3. Additional information

When using terraform apply a user can provide a identity_config section within the cluster config section of the terraform plan file. Here they can specify whether a system or user assigned managed identity is to be used for the cluster.

The default if an identity_config is not provide will be use a system assigned managed identity.

4. Special notes for your reviewer

Changes were tested by creating and modifying clusters on Olympus dev stack. Scenarios tested are summarized below:

• No identity_config struct specified: SUCCESS -> Cluster with system assigned MI
• Empty identity_config struct: SUCCESS -> Cluster with system assigned MI -> Defaults to system assigned MI in terraform plan
• identity_config struct with type IDENTITY_TYPE_SYSTEM_ASSIGNED: SUCCESS -> Cluster with system assigned MI

---

• identity_config struct with type IDENTITY_TYPE_USER_ASSIGNED and no userAssigned struct: ERROR -> No cluster -> Expected behavior, see Terraform test - User assigned identity with no userAssigned struct attachment
• identity_config struct with type IDENTITY_TYPE_USER_ASSIGNED and empty userAssigned struct: ERROR -> No cluster -> Expected behavior, see Terraform test - User assigned identity with empty struct attachment
• identity_config struct with type IDENTITY_TYPE_USER_ASSIGNED and populated userAssigned struct, invalid identity: ERROR -> No cluster -> Expected behavior, see Terraform test - User assigned identity with invalid identity attachment
• identity_config struct with type IDENTITY_TYPE_USER_ASSIGNED and populated userAssigned struct, valid identity: SUCCESS -> Cluster with user assigned MI

---

• Create cluster with system assigned MI: SUCCESS
• Create cluster with user assigned MI: SUCCESS
• Create cluster with system assigned MI, then change to a user assigned MI: SUCCESS -> List aks clusters now shows user assigned identity for cluster
• Create cluster with system assigned MI, then change to a user assigned MI, then change back to a system assigned MI: SUCCESS -> List aks cluster shows system assigned identity again for cluster; SYSTEM -> USER -> SYSTEM
• Create cluster with user assigned MI, then change to a system assigned MI: SUCCESS -> List aks clusters now shows system assigned identity for cluster
• Create cluster with user assigned MI, then change to a system assigned MI, then change back to user assigned MI: SUCCESS -> List aks cluster shows user assigned identity again for cluster; USER -> SYSTEM -> USER

---

Terraform test - User assigned identity with no userAssigned struct:

Terraform test - User assigned identity with empty struct

Terraform test - User assigned identity with invalid identity

[vmwclabot]

@gshaw-pivotal, you must sign every commit in this pull request acknowledging our Developer Certificate of Origin before your changes are merged. This can be done by adding Signed-off-by: John Doe <john.doe@email.org> to the last line of each Git commit message. The e-mail address used to sign must match the e-mail address of the Git author. Click here to view the Developer Certificate of Origin agreement.

• Commit 98f2b99 must be signed by gshaw+github@pivotal.io
• Commit 45e5d8f must be signed by gshaw+github@pivotal.io

[codecov-commenter]

Codecov Report

Attention: 12 lines in your changes are missing coverage. Please review.

Comparison is base (8c08715) 25.09% compared to head (92c4692) 25.24%.

Files	Patch %	Lines
internal/resources/akscluster/akscluster_mapper.go	75.51%	8 Missing and 4 partials ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #359      +/-   ##
==========================================
+ Coverage   25.09%   25.24%   +0.14%     
==========================================
  Files         191      191              
  Lines       16480    16529      +49     
==========================================
+ Hits         4135     4172      +37     
- Misses      12131    12139       +8     
- Partials      214      218       +4     

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

[vmwclabot]

@gshaw-pivotal, you must sign every commit in this pull request acknowledging our Developer Certificate of Origin before your changes are merged. This can be done by adding Signed-off-by: John Doe <john.doe@email.org> to the last line of each Git commit message. The e-mail address used to sign must match the e-mail address of the Git author. Click here to view the Developer Certificate of Origin agreement.

• Commit 131aeee must be signed by gshaw+github@pivotal.io

[github-actions]

I'm going to lock this pull request because it has been closed for 30 days. This helps our maintainers find and focus on the active issues.

If you have found a problem that seems related to this change, please open a new issue and complete the issue template so we can capture all the details necessary to investigate further.