#46 Remove data resource for sns topic to avoid race condition

Data Resources are evaluated before any code is executed, so if a single terraform apply intends to create an SNS topic _and_ create this module, the apply will fail because the data resource cannot resolve.  Avoiding the use of data resources by deriving the SNS manually corrects the issue in this case.

main.tf

@@ -1,8 +1,5 @@
-data "aws_sns_topic" "this" {
-  count = false == var.create_sns_topic && var.create ? 1 : 0
-
-  name = var.sns_topic_name
-}
+data "aws_caller_identity" "current" {}
+data "aws_region" "current" {}
 
 resource "aws_sns_topic" "this" {
   count = var.create_sns_topic && var.create ? 1 : 0
@@ -15,9 +12,8 @@ resource "aws_sns_topic" "this" {
 locals {
   sns_topic_arn = element(
     concat(
-      aws_sns_topic.this.*.arn,
-      data.aws_sns_topic.this.*.arn,
-      [""],
+      aws_sns_topic.this.*.id,
+      ["arn:aws:sns:${data.aws_region.current.name}:${data.aws_caller_identity.current.account_id}:${var.sns_topic_name}"],
     ),
     0,
   )