How to pass GitHub Action secrets into Terraform Azure VM Custom Data?

Question

I currently have a GitHub Actions workflow that does a terraform apply and creates an Azure VM. Terraform code is as follows:

resource "azurerm_linux_virtual_machine" "linux_vm" {
  name                = var.vm_linux_name
  resource_group_name = data.azurerm_resource_group.resource_group.name
  location            = data.azurerm_resource_group.resource_group.location
  size                = var.vm_size
  admin_username      = var.vm_admin_user

  custom_data = filebase64("test.sh")
  network_interface_ids = [
    azurerm_network_interface.vm_linux_ni.id,
  ]

  admin_ssh_key {
    username   = var.vm_admin_user
    public_key = file(var.vm_linux_admin_ssh_key)
  }

  os_disk {
    caching              = var.vm_os_disk_caching
    storage_account_type = var.vm_os_disk_sa_type
  }

  source_image_reference {
    publisher = var.vm_linux_image_publisher
    offer     = var.vm_linux_image_offer
    sku       = var.vm_linux_image_sku
    version   = var.vm_linux_image_version
  }

  identity {
    type = "SystemAssigned"
  }
}

I'm using the test.sh script as a custom data that will be ran when the VM is created. However, I need to pass some variables from my GitHub Actions Secrets in order to run some of the commands in the script. Something like:

az cloud set --name AzureCloud
az login --service-principal --username $client_id --password $client_secret --tenant $tenant_id 

Any idea how to pass values/variables into $client_id, $client_secret, $tenant_id?

I tried to to use something like

client_secret:${{ secrets.SP_SECRET }} 

in the workflow yml file but I don't think that worked.