fix: do not pass metadata_options if variable is null

[ranimbal]

Setting the metadata_options explicitly in the AWS launch template is not supported in certain regions. The error we get is:

You must use a valid fully formed launch template; specifing HttpProtocol metadata options for an instance is not supported in this region.

This fix sets the metadata_options only if the value passed in is not null.

As described in hashicorp/terraform-provider-aws#25227, version 5.0.0 of the terraform-provider-aws fixed the issue of removing default values from the launch template. Hence this fix also upgrades the AWS terraform provider to that new version.

[adamacosta]

I'm probably going to incorporate this idea into a more general rework branch. This has an issue right now, but it's also an issue in the original code. You can't set just one part of the metadata options. We really need to be doing a lookup call with a default for each individual field and not assuming all of the keys always exist in the map passed to the variable, at least not if we want the type constraint to be map(any) as is currently the case.

[ranimbal]

I'm probably going to incorporate this idea into a more general rework branch. This has an issue right now, but it's also an issue in the original code. You can't set just one part of the metadata options. We really need to be doing a lookup call with a default for each individual field and not assuming all of the keys always exist in the map passed to the variable, at least not if we want the type constraint to be map(any) as is currently the case.

Sounds good. Should I close this pull request then with a reference to the new rework issue once you create it?

[adamacosta]

You can leave it. I'll take care of the linking and closing when it happens.