Add dns_enable to variables (#38)

* Add dns_enable

* Fix if statement

* remove space

* Update variables.tf

Co-Authored-By: ommadawn46 <[email protected]>

* rebuild README

* Invalidate DNS according to the value of parent_zone_id and parent_zone_name

* Update terraform-aws-route53-alias version

Author: ommadawn46

main.tf

@@ -172,8 +172,8 @@ resource "aws_cloudfront_distribution" "default" {
 }
 
 module "dns" {
-  source           = "git::https://github.com/cloudposse/terraform-aws-route53-alias.git?ref=tags/0.2.5"
-  enabled          = "${var.enabled}"
+  source           = "git::https://github.com/cloudposse/terraform-aws-route53-alias.git?ref=tags/0.2.7"
+  enabled          = "${var.enabled == "true" && (length(var.parent_zone_id) > 0 || length(var.parent_zone_name) > 0) ? "true" : "false"}"
   aliases          = "${var.aliases}"
   parent_zone_id   = "${var.parent_zone_id}"
   parent_zone_name = "${var.parent_zone_name}"