[BUG] Microsoft.Insights Autoscale rules `metricName` require an enum for valid values.

[DanielMicrosoft]

API Spec link

https://github.com/Azure/azure-rest-api-specs/blob/main/specification/monitor/resource-manager/Microsoft.Insights/stable/2022-10-01/autoscale_API.json

API Spec version

2022-10-01

Describe the bug

MetricTrigger.MetricName should be an enum with valid values instead of a primitive string type.

Expected behavior

This creates ambiguous errors in Azure-powershell which is generated from the spec of azure-rest-api-specs.

See issue: Azure/azure-powershell#24727

Actual behavior

See issue: Azure/azure-powershell#24727

User receives generic error for the metric name, with no guidance as to what are the accepted values.

Reproduction Steps

Api call to:

PUT https://management.azure.com/subscriptions/{subscriptionId}/resourcegroups/{resourceGroup}/providers/Microsoft.Insights/autoscalesettings/test-autoscale?api-version=2022-10-01

With payload:

{
  "properties": {
    "profiles": [{
      "rules": [{
        "metricTrigger": {
          "metricName": "Percentage CPU",
          "metricNamespace": "microsoft.web/serverfarms",
          "metricResourceUri": "/subscriptions/.../providers/Microsoft.Web/serverfarms/test-asp"
        }
      }]
    }]
  }
}

Produces generic error:

Error: resource: /subscriptions/.../providers/Microsoft.Web/serverfarms/test-asp, 
       metricnamespace: microsoft.web/serverfarms, 
       metricname: Percentage CPU

Environment

Name Value

---

PSVersion 7.4.1
PSEdition Core
GitCommitId 7.4.1
OS Microsoft Windows 10.0.22631
Platform Win32NT
PSCompatibleVersions {1.0, 2.0, 3.0, 4.0…}
PSRemotingProtocolVersion 2.3
SerializationVersion 1.1.0.1
WSManStackVersion 3.0

[DanielMicrosoft]

Addresses Azure/azure-powershell#24727