PageArchive is used to delete and undelete pages. It needs to become aware of the new MCR schema.
Related Gerrit Patches:
|mediawiki/core : master||Fix undeletion write-both/read-old mode.|
|mediawiki/core : master||[MCR] Make PageArchive aware of MCR|
|mediawiki/core : master||Tests for preserving content ID and origin during undeletion|