fix: validation logic for dns_zone_name when set to null (#922)

Co-authored-by: toddgiguere <[email protected]>

Author: imprateeksh

main.tf

@@ -359,7 +359,7 @@ resource "ibm_is_flow_log" "flow_logs" {
 # ##############################################################################
 
 resource "ibm_dns_zone" "dns_zone" {
-  count       = var.enable_hub && !var.skip_custom_resolver_hub_creation && var.dns_zone_name != null ? 1 : 0
+  count       = var.enable_hub && !var.skip_custom_resolver_hub_creation && alltrue([var.dns_zone_name != null, var.dns_zone_name != ""]) ? 1 : 0
   name        = var.dns_zone_name
   instance_id = var.use_existing_dns_instance ? var.existing_dns_instance_id : ibm_resource_instance.dns_instance_hub[0].guid
   description = var.dns_zone_description

variables.tf

@@ -644,7 +644,7 @@ variable "dns_zone_name" {
   type        = string
 
   validation {
-    condition     = var.enable_hub && !var.skip_custom_resolver_hub_creation ? length(coalesce(var.dns_zone_name, "")) > 0 : true
+    condition     = var.enable_hub && !var.skip_custom_resolver_hub_creation ? alltrue([var.dns_zone_name != null, var.dns_zone_name != ""]) : true
     error_message = "dns_zone_name must not be null or empty when enable_hub is true and skip_custom_resolver_hub_creation is false."
   }