userAssignedIdentityID in azure.json is wrong when using user assinged MSI

[ArchangelSDY]

/kind bug

[Before submitting an issue, have you checked the Troubleshooting Guide?]

What steps did you take and what happened:
[A clear and concise description of what the bug is.]

1. Create a control plane AzureMachineTemplate that specifies userAssignedIdentities. For example,

apiVersion: infrastructure.cluster.x-k8s.io/v1beta1
kind: AzureMachineTemplate
metadata:
  name: foo-control-plane
  namespace: foo
spec:
  template:
    spec:
      dataDisks:
      - diskSizeGB: 256
        lun: 0
        nameSuffix: etcddisk
      identity: UserAssigned
      osDisk:
        diskSizeGB: 128
        osType: Linux
      sshPublicKey: 
      userAssignedIdentities:
      - providerID: /subscriptions/...
      - providerID: /subscriptions/...
      vmSize: Standard_F4s

2. Check the generated azure.json on control plane nodes. The userAssignedIdentityID looks like:

{
    "userAssignedIdentityId": "/subscriptions/..."
}

What did you expect to happen:
There are two issues here:

• It should be userAssignedIdentityID rather than userAssignedIdentityId
• The value should be a client id (GUID) of the MSI. Not an ARM resource ID per cloud provider doc: https://kubernetes-sigs.github.io/cloud-provider-azure/install/configs/.

Anything else you would like to add:
[Miscellaneous information that will assist in solving the issue.]

• Bug 1 location:
  

  cluster-api-provider-azure/controllers/helpers.go

  Line 373 in c3d1ef1

  UserAssignedIdentityID string `json:"userAssignedIdentityId,omitempty"`

• Bug 2 location:
  

  cluster-api-provider-azure/controllers/azurejson_machine_controller.go

  Lines 184 to 188 in c3d1ef1

  	// Construct secret for this machine
  	userAssignedIdentityIfExists := ""
  	if len(azureMachine.Spec.UserAssignedIdentities) > 0 {
  	userAssignedIdentityIfExists = azureMachine.Spec.UserAssignedIdentities[0].ProviderID
  	}

Environment:

• cluster-api-provider-azure version: v1.1.2
• Kubernetes version: (use kubectl version): 1.22
• OS (e.g. from /etc/os-release): ubuntu 20.04

[jackfrancis]

Confirmed that the value in azure.json should be the clientID of the MSI and not the resource URI

[CecileRobertMichon]

/milestone v1.3
/help

[mboersma]

/assign
/remove-help