Cluster-api-provider-azure: AzureMachinePool SpotVMOptions maxPrice property fails to serialize

[axbarsan]

/kind bug

What steps did you take and what happened:
Trying to apply an AzureMachinePool that uses spot instances and has a maximum price of 0.01.

While templating and applying the following AzureMachinePool resource via kubectl apply, everything works as expected.

'AzureMachinePool' resource

apiVersion: exp.infrastructure.cluster.x-k8s.io/v1alpha3
kind: AzureMachinePool
metadata:
  creationTimestamp: null
  labels:
    cluster.x-k8s.io/cluster-name: qqb7s
  name: 4sgq9
  namespace: adrian-test
spec:
  location: ""
  template:
    osDisk:
      diskSizeGB: 0
      managedDisk:
        storageAccountType: ""
      osType: ""
    sshPublicKey: ""
    vmSize: Standard_D4s_v3
    spotVMOptions:
      maxPrice: 0.01
status:
  ready: false
  replicas: 0

However, if I'm trying to fetch that resource using the Go controller-runtime client (v0.6.3), I get the
following error:

v1alpha3.AzureMachineTemplate.SpotVMOptions: v1alpha3.SpotVMOptions.MaxPrice: ReadString: expects " or n, but found 0

Also, if I want to apply a resource using the same configuration, but using the CAPZ types and the controller-runtime client, I get the following error:

AzureMachinePool.exp.infrastructure.cluster.x-k8s.io "4sgq9" is invalid: spec.template.spotVMOptions.maxPrice: Invalid value: "string": spec.template.spotVMOptions.maxPrice in body must be of type number: "string"

What did you expect to happen:

I expect to be able to apply and fetch the resource in the same way using the Go client as I do by writing/templating the CRD.

Anything else you would like to add:

The field maxPrice in the AzureMachinePool CRD is of type number, but in the Go CAPZ types, it it is a string pointer, that has number validation.

This can be solved by using a *resource.Quantity type in the Go code.

If you agree that this is an issue that needs fixing, I can do the implementation right away.

Environment:

• cluster-api-provider-azure version: v0.4.11
• Kubernetes version: (use kubectl version): 1.18.10 Server / 1.19.3 Client
• OS (e.g. from /etc/os-release): macOS 11.1

[CecileRobertMichon]

If you agree that this is an issue that needs fixing, I can do the implementation right away.

Yes, please go for it
/assign @axbarsan

/cc @JoelSpeed - fyi, other providers might have the same issue