fix: Correct evaluation logic when determining master_user_options arguments (#20)

Co-authored-by: Dimitri GRISARD <dimitri.grisard@ingenico.com>
Co-authored-by: Bryant Biggs <bryantbiggs@gmail.com>

Author: 3 people

main.tf

@@ -45,7 +45,7 @@ resource "aws_opensearch_domain" "this" {
         for_each = try([advanced_security_options.value.master_user_options], [{}])
 
         content {
-          master_user_arn      = try(master_user_options.value.master_user_arn, null) == null ? try(master_user_options.value.master_user_arn, data.aws_iam_session_context.current[0].issuer_arn) : null
+          master_user_arn      = try(master_user_options.value.master_user_arn, null) != null ? try(master_user_options.value.master_user_arn, data.aws_iam_session_context.current[0].issuer_arn) : null
           master_user_name     = try(master_user_options.value.master_user_arn, null) == null ? try(master_user_options.value.master_user_name, null) : null
           master_user_password = try(master_user_options.value.master_user_arn, null) == null ? try(master_user_options.value.master_user_password, null) : null
         }