fix: update name of topic used to publish CERTIFICATE_CREATED events

[APER-2347]

This PR updates the name of the topic we are publishing our `CERTIFICATE_CREATED` events to. We had put a very generic name when writing the publishing code (and this was way before the actual topic was created). Now that the Confluent configuration is ready we need to update the name in our publishing code.

lms/djangoapps/certificates/signals.py

@@ -169,7 +169,7 @@ def listen_for_certificate_created_event(sender, signal, **kwargs):
     if SEND_CERTIFICATE_CREATED_SIGNAL.is_enabled():
         get_producer().send(
             signal=CERTIFICATE_CREATED,
-            topic='certificates',
+            topic='learning-certificate-lifecycle',
             event_key_field='certificate.course.course_key',
             event_data={'certificate': kwargs['certificate']},
             event_metadata=kwargs['metadata']

lms/djangoapps/certificates/tests/test_signals.py

@@ -513,5 +513,5 @@ class CertificateEventBusTests(ModuleStoreTestCase):
         data = mock_producer.return_value.send.call_args.kwargs
         assert data['signal'].event_type == CERTIFICATE_CREATED.event_type
         assert data['event_data']['certificate'] == expected_certificate_data
-        assert data['topic'] == 'certificates'
+        assert data['topic'] == 'learning-certificate-lifecycle'
         assert data['event_key_field'] == 'certificate.course.course_key'