The URL cleanup code contains a lot of knowledge about what are or are not valid URLs, but it is only used client-side when adding URLs. Invalid URLs can still be added, or URLs that were considered valid at the time they were added can later be judged invalid (e.g. due to improvements to the validation code). Likewise, URLs can have an outdated format that the cleanup code has learned to correct in the meantime.

We should use the existing code to create a report on the server that, for all existing URLs, checks whether

• the cleanup code would (now) change the URL into something else,
• the validation code would (now) reject the URL (for the entity and relationships types it is used in).

This should not be too difficult as Postgres supports PL/V8, i.e. we can run the Javascript mostly as-is inside the database.