fix: Update cloudwatch log group creation conditional (#481)

Co-authored-by: magreenbaum <magreenbaum>

modules/db_instance/main.tf

@@ -146,8 +146,9 @@ resource "aws_db_instance" "this" {
 # CloudWatch Log Group
 ################################################################################
 
+# Log groups will not be created if using an identifier prefix
 resource "aws_cloudwatch_log_group" "this" {
-  for_each = toset([for log in var.enabled_cloudwatch_logs_exports : log if var.create && var.create_cloudwatch_log_group])
+  for_each = toset([for log in var.enabled_cloudwatch_logs_exports : log if var.create && var.create_cloudwatch_log_group && !var.use_identifier_prefix])
 
   name              = "/aws/rds/instance/${var.identifier}/${each.value}"
   retention_in_days = var.cloudwatch_log_group_retention_in_days