Install Steam on persistent data disk that is never destroyed by terraform

main.tf

@@ -54,6 +54,19 @@ resource "azurerm_network_interface" "vm_nic" {
   }
 }
 
+resource "azurerm_managed_disk" "data_disk" {
+  name                 = "${var.prefix}-winvm-datadisk"
+  location             = azurerm_resource_group.rg.location
+  resource_group_name  = azurerm_resource_group.rg.name
+  storage_account_type = "Premium_LRS"
+  create_option        = "Empty"
+  disk_size_gb         = var.datadisk_size_gb
+
+  lifecycle {
+    prevent_destroy = true
+  }
+}
+
 resource "random_password" "admin_password" {
   length  = 16
   special = false
@@ -65,6 +78,8 @@ resource "azurerm_windows_virtual_machine" "vm" {
   resource_group_name = azurerm_resource_group.rg.name
   location            = azurerm_resource_group.rg.location
   size                = var.vm_size
+  priority            = var.vm_priority
+  eviction_policy     = var.vm_priority == "Spot" ? "Deallocate" : null
 
   admin_username = var.vm_admin_username
   admin_password = random_password.admin_password.result
@@ -86,6 +101,13 @@ resource "azurerm_windows_virtual_machine" "vm" {
   }
 }
 
+resource "azurerm_virtual_machine_data_disk_attachment" "data_disk_attachment" {
+  managed_disk_id    = azurerm_managed_disk.data_disk.id
+  virtual_machine_id = azurerm_windows_virtual_machine.vm.id
+  lun                = var.datadisk_lun
+  caching            = "ReadWrite"
+}
+
 resource "azurerm_virtual_machine_extension" "provision_software" {
   name                 = "provision-software"
   virtual_machine_id   = azurerm_windows_virtual_machine.vm.id
@@ -93,9 +115,11 @@ resource "azurerm_virtual_machine_extension" "provision_software" {
   type                 = "CustomScriptExtension"
   type_handler_version = "1.10"
 
+  depends_on = [azurerm_virtual_machine_data_disk_attachment.data_disk_attachment]
+
   protected_settings = <<SETTINGS
   {    
-    "commandToExecute": "powershell -command \"[System.Text.Encoding]::UTF8.GetString([System.Convert]::FromBase64String('${base64encode(templatefile("${path.module}/scripts/provision-software.ps1.tpl", {tailscale_authkey = var.tailscale_authkey}))}')) | Out-File -filepath provision-software.ps1\" && powershell -ExecutionPolicy Unrestricted -File provision-software.ps1"
+    "commandToExecute": "powershell -command \"[System.Text.Encoding]::UTF8.GetString([System.Convert]::FromBase64String('${base64encode(templatefile("${path.module}/scripts/provision-software.ps1.tpl", { tailscale_authkey = var.tailscale_authkey, datadisk_lun = var.datadisk_lun, datadisk_drive_letter = var.datadisk_drive_letter }))}')) | Out-File -filepath provision-software.ps1\" && powershell -ExecutionPolicy Unrestricted -File provision-software.ps1"
   }
   SETTINGS
-}
+}