Just a suggestion for improvement
If you add the collection-doi field it's not used by the APA and BibTex formatters. It would be great if there was some resolution mechanism implemented that would
- Use 'doi' if it exists.
- Use 'collection-doi' if 'doi' not present.
- Use 'url' or some other identifier if neither of the above exist.
This is to ensure that at least one identifier makes it into a citation string as this greatly helps with later citation tracking.
cc @arfon