Extension to Add User Info to Notebook Metadata?

Wondering if anyone knows of a recipe or has an extension that allows a user to specify personal metadata (eg name, an identifier, etc), perhaps as arbitrary fields, via a preferences panel, and then: a) add the details as metadata to every new notebook; b) optionally add the metadata to pre-existing notebooks if it is not already there (perhaps also displaying a keep/replace/add dialogue if different metadata is already baked into the notebook).