I'm trying to create a new machine on Nutanix with terraform v0.15.0 and assign the machine to an existing project I already have (created on the UI without terraform).   
 Using the Nutanix documentation
(<https://registry.terraform.io/providers/nutanix/nutanix/latest/docs/resources/virtual_machine#project_reference>) , I was able to create a VM, but not assign it to the existing project.
Using this main.tf works, however, uncommenting the `project_reference` attribute results in the following error:

```
nutanix_virtual_machine.vm1[0]: Creating...

Error: error: {
    "api_version": "3.1",
    "code": 422,
    "message_list": [
    {
        "details": {
            "metadata": [
                "Additional properties are not allowed (u'project_reference' was unexpected)"
            ]
        },
        "message": "Request could not be processed.",
        "reason": "INVALID_REQUEST"
    }
    ],
    "state": "ERROR"
}

on main.tf line 67, in resource "nutanix_virtual_machine" "vm1":
67: resource "nutanix_virtual_machine" "vm1" {

```

Here's my code:

```
provider "nutanix" {
    username     = "user"
    password     = "pass"
    port         = 1234
    endpoint     = "ip"
    insecure     = true
    wait_timeout = 10 
}

data "nutanix_cluster" "cluster" {
    name = "NTNXCluster" 
}

data "nutanix_image" "ubuntu-clone" {
    image_name = "Ubuntu-20.04-Server"
}

variable "counter" {
    type = number
    default = 1
}

resource "nutanix_virtual_machine" "vm1" {

    name                 = "test-${count.index+1}"
    count                = var.counter
    description          = "desc"
    num_vcpus_per_socket = 2
    num_sockets          = 2
    memory_size_mib      = 4096
    guest_customization_sysprep = {}
    cluster_uuid = "my_uuid"
    nic_list {
        subnet_uuid = "my_uuid"
    }

    #project_reference = {
    # kind = "project"
    # uuid = "my_uuid"
    # name = "my_project"
    #}

    disk_list {
        data_source_reference = {
            kind = "image"
            uuid = data.nutanix_image.ubuntu-clone.id
        }
        device_properties {
            disk_address = {
                device_index = 0
                adapter_type = "SATA"
            }
        device_type = "DISK"
    }
    }
}

```