Prevent document version addition/change based on access level (stop our requesters from adding versions)

Whether accidentally or on purpose, sometimes our requesters add documents as versions of creative drafts added by the designer. Perhaps they accidentally drag-and-drop a new document on top of a document instance in Workfront.

This creates a lot of confusion and extra work for the designer and also messes up the versioning in Workfront.

Prevent users of a certain access level from being able to add a version to document instances that they don't own.