Resolve "Add for_participant manager"

Closes #243 (closed)

aleksis/apps/chronos/managers.py

@@ -879,7 +879,7 @@ class LessonEventQuerySet(PolymorphicQuerySet):
     def for_participant(self, person: Union[int, Person]) -> "LessonEventQuerySet":
         """Get all lesson events the person participates in (including amends)."""
         amended = self.filter(
-            Q(amended_by__isnull=False) | Q(groups__members=person))
+            Q(amended_by__isnull=False) | Q(groups__members=person)
         ).values_list("amended_by__pk", flat=True)
         return self.filter(
             Q(groups__members=person) | Q(pk__in=amended)