[client-connection] add a sessionid property for dbapi compatibility
To ease transition from dbapi to repoapi we need the ClientConnection to be as
compatible as possible with the dbapi. Adding this method goes in this
direction.
It'll get deprecated in the deprecation wave that will conclude the repoapi
refactoring.
related to #2503918
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.