feat: update client to match API v0.11
Implements changes from cubicweb/cubes/api!52 (merged) (version 0.11).
Also removes the TransactionBackend implementation as it is not used anymore.
Edited by Arnaud Vergnet
Implements changes from cubicweb/cubes/api!52 (merged) (version 0.11).
Also removes the TransactionBackend implementation as it is not used anymore.