asg module: Default value for variable key_name

[psibi]

The default value is an empty string which indicates the instance in the ASG has no key associated with it. This makes the key to be optionally passed when using the module.

Please also note that these are not hard requirements, but merely serve to define what maintainers are looking for in PR's. Including these will more likely lead to your PR being reviewed and accepted.

• [x] Update the changelog
• [x] Make sure that modules and files are documented. This can be done inside the module and files.
• [ ] Make sure that the module is added to tests/main.tf
• [ ] Make sure that the linting passes on CI.
• [ ] Make sure that there is an up to date example for your code:
  • For new modules this would entail example code for how to use the module or some explanation in the module readme.
  • For new examples please provide a README explaining how to run the example. It's also ideal to provide a basic makefile to use the example as well.
• [ ] Make sure that there is a manual CI trigger that can test the deployment.

[ketzacoatl]

I believe we don't have a default value here b/c we want to force the module user to define that parameter, and in doing so, we also ensure they are explicit in the case when there is no key (which is not common unless using windows).

[psibi]

Fair point!