I am a bit concerned that all the new code does not have tests. I suggest we add some basic tests following the example of how Wikibase does tests internally.
For example, SpecialListProperties is conceptually similar to SpecialMathWikibase. If we
- transform MathWikibaseConnector into a service
- transform MathWikibaseConfig into a service
- Introduce a FactoryClass for SpecialMathWikibase
- Write a test for SpecialMathWikibase
we have a solid concept to test changes that interact with wikidata.