Support area aggregation for custom polygons

app/broadcast_areas/utils.py

@@ -1,8 +1,24 @@
+from app.broadcast_areas.models import CustomBroadcastArea
+
+
 def aggregate_areas(areas):
+    areas = _convert_custom_areas_to_wards(areas)
     areas = _aggregate_wards_by_local_authority(areas)
     return areas
 
 
+def _convert_custom_areas_to_wards(areas):
+    results = set()
+
+    for area in areas:
+        if type(area) == CustomBroadcastArea:
+            results |= set(area.overlapping_electoral_wards)
+        else:
+            results |= {area}
+
+    return results
+
+
 def _aggregate_wards_by_local_authority(areas):
     return {
         area.parent if area.id.startswith('wd20-')