There are many data types that use "string" as the underlying value type, such as external ID, commons media, URL and others, which we all currently handle in the same way.

For some of these, it would be convenient for users to provide some additional data, like a URL for external ID values pointing to the resource on the external database, or the URL pointing to the File for commons media.

Here are the data types we'd want additional information (in all of these cases it's a URL, either external or to commons) for:

• external-id: create a new ExternalIdValue type with fields id and url.
• commons media type
• url
• geo-shape
• tabular-data