change boolean to a variable so it can be overriden

main.tf

@@ -70,6 +70,7 @@ variable "parameter_group" {
 }
 
 variable "kms_key_id" {}
+variable "storage_encrypted" {}
 
 variable "route53_zone" {}
 
@@ -125,7 +126,7 @@ resource "aws_db_instance" "default" {
   backup_retention_period = "${var.backup_retention_period}"
   backup_window           = "${var.backup_window}"
   maintenance_window      = "${var.maintenance_window}"
-  storage_encrypted       = true
+  storage_encrypted       = "${var.storage_encrypted}"
   kms_key_id              = "${var.kms_key_id}"
 }