Add dynu_record_import_id variable for record imports

infrastructure/terraform/dynu/variables.tf

@@ -25,3 +25,9 @@ variable "dynu_password" {
   sensitive   = true
   default     = null
 }
+
+variable "dynu_record_import_id" {
+  description = "Placeholder import ID for a single dynu_dns_record during one-at-a-time reconciliation."
+  type        = string
+  default     = "REPLACE_WITH_DYNU_RECORD_IMPORT_ID"
+}