Closes #16886: Dynamic event types (#16938)

* Initial work on #16886

* Restore GraphQL filter

* Remove namespace

* Add Event documentation

* Use MultipleChoiceField for event_types

* Fix event_types field class on EventRuleImportForm

* Fix tests

* Simplify event queue handling logic

* Misc cleanup

docs/plugins/development/events.md

@@ -0,0 +1,16 @@
+# Events
+
+Plugins can register their own custom event types for use with NetBox [event rules](../../models/extras/eventrule.md). This is accomplished by calling the `register()` method on an instance of the `Event` class. This can be done anywhere within the plugin. An example is provided below.
+
+```python
+from django.utils.translation import gettext_lazy as _
+from netbox.events import Event, EVENT_TYPE_SUCCESS
+
+Event(
+    name='ticket_opened',
+    text=_('Ticket opened'),
+    type=EVENT_TYPE_SUCCESS
+).register()
+```
+
+::: netbox.events.Event