[test] Make test_undo_api less random
The order in which hooks are run is not predictable if they have the
same 'order' attribute, which is the case for SetOwnershipHook and
SetInitialStateHook. So don't assume in_state will be set before
created_by.
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.