Clarify delay_on_commit documentation doesn't return the task ID

docs/django/first-steps-with-django.rst

@@ -206,6 +206,11 @@ This API takes care of wrapping the call into the `on_commit`_ hook for you.
 In rare cases where you want to trigger a task without waiting, the existing
 :meth:`~celery.app.task.Task.delay` API is still available.
 
+One key difference compared to the ``delay`` method, is that ``delay_on_commit``
+will NOT return the task ID back to the caller. The task is not sent to the broken
+when you call the method, only when the Django transaction finishes. If you need the
+task ID, best to stick to :meth:`~celery.app.task.Task.delay`.
+
 This task class should be used automatically if you've follow the setup steps above.
 However, if your app :ref:`uses a custom task base class <task-custom-classes>`,
 you'll need inherit from :class:`~celery.contrib.django.task.DjangoTask` instead of