Added conditional project designation feature for relevant modules.

modules/linux-vm/main.tf

@@ -1,7 +1,10 @@
+data "google_client_config" "default" {}
+
 resource "google_compute_instance" "vm_hub" {
   name           = var.name
   machine_type   = var.machine_type
   can_ip_forward = var.can_ip_forward
+  project        = var.project_id != null ? var.project_id : data.google_client_config.default.project
   description    = var.description
 
   boot_disk {
@@ -11,8 +14,9 @@ resource "google_compute_instance" "vm_hub" {
   }
 
   network_interface {
-    network    = var.network_name
-    subnetwork = var.subnet_name
+    network            = var.network_name
+    subnetwork         = var.subnet_name
+    subnetwork_project = var.project_id != null ? var.project_id : data.google_client_config.default.project
   }
 
   metadata = {