This should probably not be part of the Wikibase repository, but rather ... live somewhere on GitHub and then be attached to the next release?
Acceptance criteria:
- There is a script to print the new-style config, based on the wiki’s existing legacy config
- The script uses the old legacy config parser (to be removed in the upcoming release)
- The script is either included or linked in the release notes, with instructions to run it before upgrading the Wikibase code (since the script uses the parser that only exists in the “old” release)