update due code review

Author: lonegunmanb

main.tf

@@ -573,7 +573,7 @@ resource "azurerm_kubernetes_cluster" "main" {
     }
     precondition {
       condition     = var.brown_field_application_gateway_for_ingress == null || var.green_field_application_gateway_for_ingress == null
-      error_message = "Either one of `var.existing_application_gateway_for_ingress` or `var.new_application_gateway_for_ingress` must be `null`."
+      error_message = "Either one of `var.brown_field_application_gateway_for_ingress` or `var.green_field_application_gateway_for_ingress` must be `null`."
     }
   }
 }

variables.tf

@@ -472,6 +472,10 @@ variable "green_field_application_gateway_for_ingress" {
   * `subnet_cidr` - (Optional) The subnet CIDR to be used to create an Application Gateway, which in turn will be integrated with the ingress controller of this Kubernetes Cluster.
   * `subnet_id` - (Optional) The ID of the subnet on which to create an Application Gateway, which in turn will be integrated with the ingress controller of this Kubernetes Cluster.
 EOT
+  validation {
+    condition     = var.green_field_application_gateway_for_ingress == null ? true : (can(coalesce(var.green_field_application_gateway_for_ingress.subnet_id, var.green_field_application_gateway_for_ingress.subnet_cidr)))
+    error_message = "One of `subnet_cidr` and `subnet_id` must be specified."
+  }
 }
 
 variable "http_application_routing_enabled" {