Change type of iam_bindings variable to allow multiple conditional bindings (#1658)

* modules

* fast

* dns readme

modules/folder/variables.tf

@@ -51,9 +51,10 @@ variable "iam" {
 }
 
 variable "iam_bindings" {
-  description = "Authoritative IAM bindings in {ROLE => {members = [], condition = {}}}."
+  description = "Authoritative IAM bindings in {KEY => {role = ROLE, members = [], condition = {}}}. Keys are arbitrary."
   type = map(object({
     members = list(string)
+    role    = string
     condition = optional(object({
       expression  = string
       title       = string