AC:
- dedicated wblmergelexemes endpoint
- should not include ignoreconflicts (for now)
Pointers:
- http://default.web.mw.localhost:8087/mediawiki/api.php?action=help&modules=wbmergeitems
- T198105 should be finished first so the MergerInteractor created there can be used.
- Registrar registers $wgAPIModules that will need to be extended