Draft: Resolve "Class absences: Lessons with multiple classes are marked as cancelled even if only one of the classes is absent"

Closes #63

aleksis/apps/untis/util/mysql/importers/absences.py

@@ -165,6 +165,11 @@ def import_absences(
                 )
 
                 for lesson_period in lesson_periods:
+                    if set([l_group.pk for l_group in lesson_period.lesson.groups.all()]) != set(
+                        [group.pk]
+                    ):
+                        # Cancel lesson only if this lesson is just for the absent group
+                        continue
                     week = CalendarWeek.from_date(current_date)
                     sub, __ = chronos_models.LessonSubstitution.objects.get_or_create(
                         lesson_period=lesson_period,