Changes account name to account alias so that it can be optional.

base/iam/main.tf

@@ -1,6 +1,6 @@
 module "iam_roles" {
   source = "../../submodules/iam/child_account_roles"
-  account_alias = var.account_name
+  account_alias = var.account_alias
 
   assume_role_trusted_arns  = [
     "arn:${var.aws_partition}:iam::${var.common_services_account}:role/user/mdr_engineer_readonly",

base/iam/vars.tf

@@ -3,7 +3,7 @@
 # ----------------------------------
 # Below this line are variables inherited from higher levels, so they
 # do not need to be explicitly passed to this module.
-variable "account_name" {
+variable "account_alias" {
   type = string
 }