feat: Add IP Alias Range feature on compute instance module (#233)

* Add new variable alias_ip_range default to empty slice in the compute_instance module to allow instances to set Google IP Alias Range

* Rename variable alias_ip_range to alias_ip_ranges as per Morgante's request

* Fix variable type usage

* Instance template module should not be changed

* Revert change in the example too

* Fix param name

modules/compute_instance/README.md

@@ -17,6 +17,7 @@ See the [simple](https://github.com/terraform-google-modules/terraform-google-vm
 |------|-------------|------|---------|:--------:|
 | access\_config | Access configurations, i.e. IPs via which the VM instance can be accessed via the Internet. | <pre>list(object({<br>    nat_ip       = string<br>    network_tier = string<br>  }))</pre> | `[]` | no |
 | add\_hostname\_suffix | Adds a suffix to the hostname | `bool` | `true` | no |
+| alias\_ip\_ranges | (Optional) An array of alias IP ranges for this network interface. Can only be specified for network interfaces on subnet-mode networks. | <pre>list(object({<br>    ip_cidr_range         = string<br>    subnetwork_range_name = string<br>  }))</pre> | `[]` | no |
 | deletion\_protection | Enable deletion protection on this instance. Note: you must disable deletion protection before removing the resource, or the instance cannot be deleted and the Terraform run will not complete successfully. | `bool` | `false` | no |
 | hostname | Hostname of instances | `string` | `""` | no |
 | hostname\_suffix\_separator | Separator character to compose hostname when add\_hostname\_suffix is set to true. | `string` | `"-"` | no |

modules/compute_instance/main.tf

@@ -67,6 +67,13 @@ resource "google_compute_instance_from_template" "compute_instance" {
         }
       }
     }
+    dynamic "alias_ip_range" {
+      for_each = var.alias_ip_ranges
+      content {
+        ip_cidr_range         = alias_ip_range.value.ip_cidr_range
+        subnetwork_range_name = alias_ip_range.value.subnetwork_range_name
+      }
+    }
   }
 
   source_instance_template = var.instance_template

modules/compute_instance/variables.tf

@@ -86,3 +86,12 @@ variable "deletion_protection" {
   description = "Enable deletion protection on this instance. Note: you must disable deletion protection before removing the resource, or the instance cannot be deleted and the Terraform run will not complete successfully."
   default     = false
 }
+
+variable "alias_ip_ranges" {
+  description = "(Optional) An array of alias IP ranges for this network interface. Can only be specified for network interfaces on subnet-mode networks."
+  type = list(object({
+    ip_cidr_range         = string
+    subnetwork_range_name = string
+  }))
+  default = []
+}