Tasks: set default assigned_to to {users: []}.

When the task is assigned to a user, this prevents a change of
'assigned_to' to a dict {users: [user_id]}. Instead, the
activity will be registered on 'assigned_to.users', which is nicer.

attract/tasks/eve_hooks.py

@@ -177,16 +177,21 @@ def activity_after_deleting_task(task):
 
 
 @only_for_task
-def create_shortcode(task):
+def set_defaults(task):
     from attract import shortcodes
 
     shortcode = shortcodes.generate_shortcode(task['project'], task['node_type'], u'T')
-    task.setdefault('properties', {})['shortcode'] = shortcode
+    task_properties = task.setdefault('properties', {})
+    task_properties['shortcode'] = shortcode
+
+    # When the task is assigned to a user, this prevents a change of 'assigned_to' to a dict.
+    # Instead, the activity will be registered on 'assigned_to.users', which is nicer.
+    task_properties.setdefault('assigned_to', {u'users': []})
 
 
-def create_shortcodes(nodes):
+def nodes_set_defaults(nodes):
     for node in nodes:
-        create_shortcode(node)
+        set_defaults(node)
 
 
 def setup_app(app):
@@ -195,6 +200,6 @@ def setup_app(app):
 
     app.on_replaced_nodes += activity_after_replacing_task
     app.on_inserted_nodes += activity_after_creating_tasks
-    app.on_insert_nodes += create_shortcodes
+    app.on_insert_nodes += nodes_set_defaults
     app.on_deleted_item_nodes += activity_after_deleting_task
     app.on_deleted_resource_nodes += activity_after_deleting_task