Synchronise badges with Blender ID

Synchronisation is performed in the background by the Celery Beat, every
10 minutes. It has a time limit of 9 minutes to prevent multiple refresh
tasks from running at the same time.

Synchronisation is also possible with the `manage.py badges sync` CLI
command, which can sync either a single user or all users.

pillar/__init__.py

@@ -477,6 +477,7 @@ class PillarServer(BlinkerCompatibleEve):
 
         # Pillar-defined Celery task modules:
         celery_task_modules = [
+            'pillar.celery.badges',
             'pillar.celery.email_tasks',
             'pillar.celery.file_link_tasks',
             'pillar.celery.search_index_tasks',