Event Streams SSE subscription always deserializes events to `_UnknownValue`

Start at managementApi().events().subscribe(...) and inspect the unit test and potential fix in linked pull request #896. Verify that emitted events populate typed variants such as getUserUpdated() or getOffsetOnly() rather than always becoming _UnknownValue, and run the regression test against the SSE response handling.

Checklist

• I have looked into the Readme and Examples, and have not found a suitable solution or answer.
• I have looked into the API documentation and have not found a suitable solution or answer.
• I have searched the issues and have not found a suitable solution or answer.
• I have searched the Auth0 Community forums and have not found a suitable solution or answer.
• I agree to the terms within the Auth0 Code of Conduct.

Description

When subscribing to the Event Streams SSE endpoint via managementApi().events().subscribe(...), every emitted event is deserialized to EventStreamSubscribeEventsResponseContent._UnknownValue with type: null and value: null, regardless of the actual event type. The typed variants (e.g. getUserUpdated(), getOffsetOnly()) are therefore never populated, and _isUnknown() is always true, so consumers have no way to read the event payload.

I've created a PR that shows the bug with an unit-test and a potential fix: https://github.com/auth0/auth0-java/pull/896

Reproduction

Example code to reproduce the bug:

	private void connect()
	{
		final SubscribeEventsRequestParameters.Builder settings = SubscribeEventsRequestParameters.builder()
			.eventType(EventStreamSubscribeEventsEventTypeEnum.USER_UPDATED);

		final Optional<String> offset = syncService.getOffset(EVENT_TYPE_KEY);
		if (offset.isPresent())
		{
			settings.from(offset.get());
		}
		else
		{
			settings.fromTimestamp(startOfDay());
		}

		log.info("Subscribing to Auth0 user.updated event stream (resuming from {})", offset.map(o -> "offset " + o).orElse("start of day"));
		final Iterable<EventStreamSubscribeEventsResponseContent> stream = apiProvider.getManagementApi().events().subscribe(settings.build());
		try
		{
			for (EventStreamSubscribeEventsResponseContent event : stream)
			{
				try
				{
					handleEvent(event);
				}
				catch (Exception e)
				{
					// A single malformed event must not tear down the whole stream.
					log.error("Failed to handle Auth0 event", e);
				}
			}
		}
		finally
		{
			closeQuietly(stream);
		}
	}

	private void handleEvent(EventStreamSubscribeEventsResponseContent event)
	{
		if (event.getUserUpdated().isPresent())
		{
			handleUserUpdated(event.getUserUpdated().get());
			return;
		}
		if (event.getOffsetOnly().isPresent())
		{
			handleOffsetOnly(event.getOffsetOnly().get());
			return;
		}
		if (event._isUnknown())
		{
			log.warn("Received unknown Auth0 event type, ignoring: {}", event);
		}
	}

All events will print Received unknown Auth0 event type, ignoring: EventStreamSubscribeEventsResponseContent{type: null, value: null}
(Trigger update-events by updating users in Auth0)

I've also created a unit test that reproduces the bug.
https://github.com/auth0/auth0-java/pull/896/changes#diff-7bcc14b70df7dcbb2aeae35c7e142483c5d1cf4117239559729c1a41b312139d

Additional context

No response

auth0-java version

3.10.0

Java version

21