Allow to filter subevents by sales channel

doc/api/resources/subevents.rst

@@ -474,6 +474,7 @@ Endpoints
    :query is_future: If set to ``true`` (``false``), only events that happen currently or in the future are (not) returned.
    :query is_past: If set to ``true`` (``false``), only events that are over are (not) returned.
    :query ends_after: If set to a date and time, only events that happen during of after the given time are returned.
+   :query sales_channel: If set to a sales channel identifier, the response will only contain subevents from events available on this sales channel.
    :param organizer: The ``slug`` field of a valid organizer
    :param event: The ``slug`` field of the event to fetch
    :statuscode 200: no error

src/pretix/api/views/event.py

@@ -321,6 +321,7 @@ with scopes_disabled():
         is_future = django_filters.rest_framework.BooleanFilter(method='is_future_qs')
         ends_after = django_filters.rest_framework.IsoDateTimeFilter(method='ends_after_qs')
         modified_since = django_filters.IsoDateTimeFilter(field_name='last_modified', lookup_expr='gte')
+        sales_channel = django_filters.rest_framework.CharFilter(method='sales_channel_qs')
 
         class Meta:
             model = SubEvent
@@ -353,6 +354,9 @@ with scopes_disabled():
             else:
                 return queryset.exclude(expr)
 
+        def sales_channel_qs(self, queryset, name, value):
+            return queryset.filter(event__sales_channels__contains=value)
+
 
 class SubEventViewSet(ConditionalListView, viewsets.ModelViewSet):
     serializer_class = SubEventSerializer