Add explaining comment to migration

aleksis/core/migrations/0047_add_room_model.py

@@ -18,6 +18,9 @@ class Migration(migrations.Migration):
         ('core', '0046_notification_create_field_icon'),
     ]
 
+    # This migration must run after Chronos' migration 1 through 12, but before
+    #  13. That's because we are in fact moving a model, and we need to make sure
+    #  that this migration runs at the right time.
     if "chronos" in apps.app_configs:
         recorder = migrations.recorder
         applied = False