Consider a variable that makes the module/resources optional

[lorengordon]

Since terraform doesn't support using count on modules (open issue), it is rather difficult to optionally include a module in a terraform config. The pattern I've seen to work around this has been to expose a new variable, maybe something like create_module or create_lambda, and use that to interpolate the count in every resource within the module. Yeah, it's a bit ugly.

Here's an example of what I mean:

• https://github.com/terraform-aws-modules/terraform-aws-vpc#conditional-creation

In particular, I find I need to do this rather often when writing configs that need to work both in the commercial regions and in the GovCloud regions. Since GovCloud is missing a lot of services, I need a way to make certain resources optional when it's the target region.

I'd be willing to work this if you like.