Update docs with confval definitions

[fmigneault]

Description

Currently, configuration settings are defined using custom definitions. For example:

weaver/docs/source/configuration.rst

Lines 106 to 117 in 72cc7d5

	- | ``weaver.wps = true|false`` [:class:`bool`-like]
	| (default: ``true``)
	|
	| Enables the WPS-1/2 endpoint.
	.. seealso::
	:ref:`wps_endpoint`
	.. warning::
	At the moment, this setting must be ``true`` to allow :term:`Job` execution as the worker monitors this endpoint.
	This could change with future developments (see issue `#21 <https://github.com/crim-ca/weaver/issues/21>`_).

Sphinx provides a way to define confval directives, which can be referenced by :confval:`<ref>`.
This can be used to fix current workarounds using :ref: or `<ref>`_ references pointing at custom anchors before those settings, while providing nicer rendering.

Using confval allows to directly making use of the directive to define :type: and :default::

.. confval:: the_answer
   :type: ``int`` (a *number*)
   :default: **42**

   This is a setting that controls the value of the answer.

Which would be rendered as:

---

the_answer¶

Type:

int (a number)

Default:

42

This is a setting that controls the value of the answer.

---

References

• https://www.sphinx-doc.org/en/master/usage/domains/standard.html#directive-confval