Add machine variable to terraform module (#179)

* add variable machine to enable/disable secure boot

* add role description

terraform/libvirt/modules/instance_group/main.tf

@@ -16,7 +16,7 @@ resource "libvirt_domain" "instance_group" {
   count   = var.amount
   memory  = var.memory
   vcpu    = var.vcpus
-  machine = "q35"
+  machine = var.machine
   tpm {
     backend_type    = "emulator"
     backend_version = "2.0"

terraform/libvirt/modules/instance_group/variables.tf

@@ -44,5 +44,11 @@ variable "boot_volume_id" {
 }
 
 variable "role" {
-  type = string
+  type        = string
+  description = "role of the node in the constellation. either 'control-plane' or 'worker'"
+}
+
+variable "machine" {
+  type        = string
+  description = "machine type. use 'q35' for secure boot and 'pc' for non secure boot. See 'qemu-system-x86_64 -machine help'"
 }