Register base event for ICEKitURLField

Make ICEkit Event items available in the `ICEKitURLField` customisation
of `AnyUrlField`.

icekit_events/apps.py

@@ -8,6 +8,10 @@
 from django.apps import AppConfig
 from django.utils.module_loading import autodiscover_modules
 
+from any_urlfield.forms import SimpleRawIdWidget
+
+from icekit.fields import ICEkitURLField
+
 
 class AppConfig(AppConfig):
     name = '_'.join(__name__.split('.')[:-1])
@@ -17,3 +21,7 @@ class AppConfig(AppConfig):
     def ready(self):
         # look through installed apps to see what event types are registered
         autodiscover_modules('event_type_plugins')
+
+        from .models import EventBase
+        ICEkitURLField.register_model(
+            EventBase, widget=SimpleRawIdWidget(EventBase), title='Event')