[session] move context manager logic in the security context manager
The `init_security` and `reset_security` method have no other user that the context manager itself. Having dedicated public function is not useful.
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.