Support the new Wikibase REST API

[wetneb]

There is new API, more RESTful, to retrieve and edit Wikibase entities.
The old API should hopefully stay around for a while, so for WDTK there should not be an urge to migrate, but I assume they do not intend to maintain two APIs for eternity. Also, the changes look sensible and are supportworthy, so probably worth adopting.

There are differences in JSON serialization which might cause some headaches if we want to keep supporting both serialization formats:
https://doc.wikimedia.org/Wikibase/master/php/rest_data_format_differences.html

[lydiapintscher]

I think this would be pretty cool obviously ;-) But just to be clear on the time horizon: Deprecation of the Wikibase pieces of the action API is still quite a bit out (definitely more than a year, likely quite a bit longer even). There will be announcements with plenty of time in advance.
That being said, now would be a perfect time to do some testing and give feedback to steer things into a direction that works for you. So if you have any feedback please to leave it on the feedback page.

[wetneb]

Thanks! I left some feedback there: https://www.wikidata.org/wiki/Wikidata_talk:REST_API#Datavalue_types_and_consistency_with_the_JSON_dump