[notification] introduce an official `notify_on_commit` function
It provides a proper notification api instead of replacing it by yet another
clumsy one.
Closes #2837251
Add some entities
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As manager, you can access to entity creation forms by using the `site management`_ page.
.. _`site management`: manage
As regular user, the index page or the action box may propose some links to create entities according to the context.