API: Allow to filter events by attributes (#1466)

* Allow filtern events-ressource on API by attrs

* Document meta-data attr-filter for order resource

* Actually document the change and not some random other nonsensical thing...

* Doc for subevent-filtering

* Test for attr-filtering on events resource

* Allow attr-filtering on subevents

* Add attr-filter test for subevent

* Update doc/api/resources/subevents.rst

* Update src/tests/api/test_subevents.py

* Update doc/api/resources/events.rst

src/pretix/api/views/event.py

@@ -18,6 +18,7 @@ from pretix.base.models import (
 )
 from pretix.base.models.event import SubEvent
 from pretix.helpers.dicts import merge_dicts
+from pretix.presale.views.organizer import filter_qs_by_attr
 
 with scopes_disabled():
     class EventFilter(FilterSet):
@@ -85,6 +86,8 @@ class EventViewSet(viewsets.ModelViewSet):
                 organizer=self.request.organizer
             )
 
+        qs = filter_qs_by_attr(qs, self.request)
+
         return qs.prefetch_related(
             'meta_values', 'meta_values__property', 'seat_category_mappings'
         )
@@ -241,6 +244,9 @@ class SubEventViewSet(ConditionalListView, viewsets.ModelViewSet):
                 event__organizer=self.request.organizer,
                 event__in=self.request.user.get_events_with_any_permission()
             )
+
+        qs = filter_qs_by_attr(qs, self.request)
+
         return qs.prefetch_related(
             'subeventitem_set', 'subeventitemvariation_set', 'seat_category_mappings'
         )