CORE-1955 Add AppVersionOrderRequest schema and docs

[psarando]

This PR will add the AppVersionOrderRequest schema and docs.

The AppVersionOrderRequest expects the app versions to be in descending order, with the newest (or latest) first, since that is also the way they are listed in the app details and listing endpoints.

[ianmcorvidae]

LGTM. I guess we're allowing the :version key but setting it optional since it won't be used by the endpoint in the apps PR. Seems fine, in any case.

[psarando]

LGTM. I guess we're allowing the :version key but setting it optional since it won't be used by the endpoint in the apps PR. Seems fine, in any case.

Right, sometimes it's easier for the UI to reuse the same format as what it gets from a GET endpoint in a POST/PUT endpoint, but the :version labels are not needed for the reordering update.

[psarando]

Thanks for the reviews! 👍