tools (datetime, utils): fix incorrect use of naive object: `tools.datetime.format_datetime` was expecting aware datetime objects while `tools.utils.xmpp_date` was returning naive datetime objects. A check has been added to the former one, and latter one has been modified to return aware datetime objects.

.. _contributing:

============
contributing
============

This part of the documentation is for people willing to contribute to the development of
Libervia and its ecosystem, it is not needed to read this if you only plan to use the
software.

.. toctree::
   :glob:
   :maxdepth: 2

   testing