`ManagedClusterUpgradeProfileProperties.agentPoolProfiles` is not marked as nullable

https://github.com/Azure/azure-sdk-for-rust/blob/8530b14828869e93f200894c7f79b6be3a3ed5e3/services/mgmt/containerservice/src/package_2021_03/models.rs#L1019-L1024

I can query this part of the API via a route such as azure_mgmt_containerservice::operations::managed_clusters::get_upgrade_profile().

Depending on the resources, of course, but I can get a null ("agentPoolProfiles": null) result for ManagedClusterUpgradeProfileProperties.agentPoolProfiles. This API/SDK will then error out during deserialization, throwing a:

Error: DeserializeError { source: Error("invalid type: null, expected a sequence", line: 18, column: 28)

for a JSON response like:

{
  "id": "/subscriptions/decafbad-d3ad-b33f-b000-deadf00dba11/resourcegroups/RedactedGroup/providers/Microsoft.ContainerService/managedClusters/RedactedCluster/upgradeprofiles/default",
  "name": "default",
  "type": "Microsoft.ContainerService/managedClusters/upgradeprofiles",
  "properties": {
   "controlPlaneProfile": {
    "kubernetesVersion": "1.18.17",
    "osType": "Linux",
    "upgrades": [
     {
      "kubernetesVersion": "1.19.7"
     },
     {
      "kubernetesVersion": "1.19.9"
     }
    ]
   },
   "agentPoolProfiles": null
  }
 }

Therefore, I believe this field (both, probably?) should be marked as an Option and skip_serializing_if = "Option::is_none")

However - this might be an error on the upstream api spec? re: https://github.com/Azure/azure-rest-api-specs/blob/1b0ed8edd58bb7c9ade9a27430759527bd4eec8e/specification/containerservice/resource-manager/Microsoft.ContainerService/stable/2020-03-01/managedClusters.json#L2187-L2193, it's not marked "x-nullable": true or non-required.

Azure / azure-sdk-for-rust

`ManagedClusterUpgradeProfileProperties.agentPoolProfiles` is not marked as nullable #265