Fix linting

modules/net-vpn-ha/variables.tf

@@ -25,6 +25,7 @@ variable "network" {
 }
 
 variable "peer_gateway" {
+  description = "Configuration of the (external or GCP) peer gateway."
   type = object({
     external = optional(object({
       redundancy_type = string
@@ -34,8 +35,8 @@ variable "peer_gateway" {
   })
   nullable = false
   validation {
-    condition     = var.peer_gateway.external != null || var.peer_gateway.gcp != null
-    error_message = "TODO"
+    condition     = (var.peer_gateway.external != null) != (var.peer_gateway.gcp != null)
+    error_message = "Peer gateway configuration must define exactly one between `external` and `gcp`."
   }
 }
 
@@ -50,6 +51,7 @@ variable "region" {
 }
 
 variable "router_config" {
+  description = "Cloud Router configuration for the VPN. If you want to reuse an existing router, set create to false and use name to specify the desired router."
   type = object({
     create    = optional(bool, true)
     asn       = number