[Meta issue] Structural improvements

[fehguy]

As we look at the next version of the Open API specification, there are structural improvements that can definitely be made. This is a meta issue for tracking improvements for the basic OpenAPI specification structure.

Please don't add comments to this issue--rather open new tickets, if they apply, and reference this as the parent.

[handrews]

This meta-issue has served its purpose, and any remaining items are being tracked under new labeling now, mostly the various re-use: * lables and/or metadata. Major structural changes are now being considered in the sig-moonwalk repository.