add information about logging

source/development/index.rst

@@ -21,6 +21,7 @@ As Chill rely on the `symfony <http://symfony.com>`_ framework, reading the fram
     Access control model <access_control_model.rst>
     Messages to users <messages-to-users.rst>
     Localisation <localisation.rst>
+    Logging <logging.rst>
     Database migrations <migrations.rst>
     Searching <searching.rst>
     Timelines <timelines.rst>

source/development/logging.rst

@@ -0,0 +1,50 @@
+.. Copyright (C)  2016 Champs Libres Cooperative SCRLFS
+   Permission is granted to copy, distribute and/or modify this document
+   under the terms of the GNU Free Documentation License, Version 1.3
+   or any later version published by the Free Software Foundation;
+   with no Invariant Sections, no Front-Cover Texts, and no Back-Cover Texts.
+   A copy of the license is included in the section entitled "GNU
+   Free Documentation License".
+
+
+Logging
+*******
+
+.. seealso::
+   
+   Symfony documentation: `How to user Monolog to write logs <http://symfony.com/doc/current/cookbook/logging/monolog.html>`_
+      The symfony cookbook page about logging.
+
+
+A channel for custom logging has been created to store sensitive data. 
+
+The channel is named ``chill``. 
+
+The installer of chill should be aware that this channel may contains sensitive data and encrypted during backup.
+
+Logging to channel `chill`
+============================
+
+You should use the service named ``chill.main.logger``, as this : 
+
+.. code-block:: php
+
+   $logger = $this->get('chill.main.logger');
+
+You should store data into context, not in the log himself, which should remains the same for the action. 
+
+Example of usage : 
+
+.. code-block:: php
+
+   $logger->info("An action has been performed about a person", array(
+      'person_lastname' => $person->getLastName(),
+      'person_firstname' => $person->getFirstName(),
+      'person_id' => $person->getId(),
+      'by_user' => $user->getUsername()
+   ));
+
+For further processing, it is a good idea to separate all fields (like firstname, lastname, ...) into different context keys.
+
+By convention, you should store the username of the user performing the action under the ``by_user`` key.
+