Improve documentation

This commit adds a lot of documentation including block diagramms for
message flows.

gnuviechadmin/osusers/admin.py

@@ -1,6 +1,10 @@
 """
 This module contains the Django admin classes of the :py:mod:`osusers` app.
 
+The module starts Celery_ tasks.
+
+.. _Celery: http://www.celeryproject.org/
+
 """
 from django import forms
 from django.utils.translation import ugettext_lazy as _
@@ -341,6 +345,30 @@ class SshPublicKeyAdmin(admin.ModelAdmin):
         :param request: the current HTTP request
         :param queryset: Django ORM queryset representing the selected ssh keys
 
+        This method starts a Celery_ task to update the list of authorized keys
+        for each affected user.
+
+        .. blockdiag::
+            :desctable:
+
+            blockdiag {
+                node_width = 200;
+
+                A -> B;
+
+                A [ label = "", shape = beginpoint,
+                    description = "this method"
+                ];
+                B [ label = "set file ssh authorized_keys",
+                    description = ":py:func:`set_file_ssh_authorized_keys()
+                    <fileservertasks.tasks.set_file_ssh_authorized_keys>`
+                    called with username and a list of keys, returning the path
+                    of the ssh authorized_keys file",
+                    color = "LightGreen",
+                    stacked
+                ];
+            }
+
         """
         users = set([
             item['user'] for item in