Add missing IAM authentication variables to root module

- Add redis_enable_iam_auth variable for Redis IAM authentication control
- Add db_iam_username variable for PostgreSQL IAM username specification
- Required for PostgreSQL passwordless authentication tests

Author: raviharshicorp

variables.tf

@@ -889,3 +889,16 @@ variable "extern_vault_token_renew" {
   type        = number
   description = "(Optional if var.extern_vault_enable = true) How often (in seconds) to renew the Vault token."
 }
+
+# IAM Authentication variables
+variable "redis_enable_iam_auth" {
+  type        = bool
+  default     = false
+  description = "Whether to enable IAM authentication for Redis. Used for passwordless authentication."
+}
+
+variable "db_iam_username" {
+  type        = string
+  default     = null
+  description = "The IAM username for database authentication. Required when postgres_enable_iam_auth is true."
+}