Azure ARM API and Terraform Provider behavior mismatch for AKS private DNS zone id variable

[DewinGoh]

Terraform (and AzureRM Provider) Version

Terraform Version: 0.13.7
Azurerm Provider Version: >= 2.47.0

Affected Resource(s)

• azurerm_kubernetes_cluster

Hi, we note that there is some discrepancy between the Azure API and the terraform provider behavior. Specifically, we note that when you do not provide a value for private DNS Zone ID, the Azure ARM API will generate a default value "system", and not "System" as seen in https://github.com/terraform-providers/terraform-provider-azurerm/blob/master/azurerm/internal/services/containers/kubernetes_cluster_resource.go#L529

However, the terraform provider has a value check that enforces "System" rather than "system" - which is different from the default generated value via the Azure API. Terraform sees "system" and "System" as two different values and forces recreation of clusters, which is not what we wish for

We encountered this issue when we started to define the variable properly via terraform as opposed to leaving it as a null variable. This would impact all users who have had clusters which did not define this variable previously and is now opting to define it.

Would like to check if there is a misconception here - if this bug is validated, we'll be more than happy to do up the MR. Thanks!

[github-actions]

This functionality has been released in v2.83.0 of the Terraform Provider. Please see the Terraform documentation on provider versioning or reach out if you need any assistance upgrading.

For further feature requests or bug reports with this functionality, please create a new GitHub issue following the template. Thank you!

[tombuildsstuff]

Fixed via #13000

[github-actions]

This functionality has been released in v2.83.0 of the Terraform Provider. Please see the Terraform documentation on provider versioning or reach out if you need any assistance upgrading.

For further feature requests or bug reports with this functionality, please create a new GitHub issue following the template. Thank you!

[github-actions]

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