It's not really a policy but because of the way it's defined in the structure of a CloudFormation template it seems like this is the best place to define it. The metadata section can be any arbitrary json so the spec for it has to be loose. Depending on the resource it could be one of these metadata keys. For those, we can define a proper spec for them. For now I'll leave that for another pull request.
Add support for adding a metadata section to resources. https://docs.aws.amazon.com/AWSCloudFormation/latest/UserGuide/metadata-section-structure.html
It's not really a policy but because of the way it's defined in the structure of a CloudFormation template it seems like this is the best place to define it. The metadata section can be any arbitrary json so the spec for it has to be loose. Depending on the resource it could be one of these metadata keys. For those, we can define a proper spec for them. For now I'll leave that for another pull request.