[server] extract creating a new cnxset in a _new_cnxset() helper
So we can move logic specific to _CnxSetPool here.
.. _auth_module:
:mod:`cubicweb.pyramid.auth`
----------------------------
.. automodule:: cubicweb.pyramid.auth
.. autofunction:: includeme
.. autoclass:: UpdateLoginTimeAuthenticationPolicy
:show-inheritance:
:members: