[notification] use new style operation for notification This results in far less operations created. Operation creation is expensive. We keep some compatibility with the previous API because some cubes have been reported to use it.

[cleanup] drop code deprecated since 3.6 The 3.6 API have been dropped some time ago. Those three lines survived the purge. One of them is even deprecated since 3.5.

[notification] fix documentation The doc say precommit, the code says postcommit. The code is right. We also clarify the documentation of another related operation looking suspiciously wrong but actually correct.