fix: don’t force REST API consumers to set repetition_of for timeslots

program/serializers.py

@@ -661,7 +661,9 @@ class ScheduleDryRunResponseSerializer(serializers.Serializer):
 class TimeSlotSerializer(serializers.ModelSerializer):
     show = serializers.PrimaryKeyRelatedField(queryset=Show.objects.all())
     schedule = serializers.PrimaryKeyRelatedField(queryset=Schedule.objects.all())
-    repetition_of = serializers.PrimaryKeyRelatedField(queryset=TimeSlot.objects.all())
+    repetition_of = serializers.PrimaryKeyRelatedField(
+        queryset=TimeSlot.objects.all(), allow_null=True
+    )
 
     class Meta:
         model = TimeSlot