_maybe_auto_commit_offsets_async doesn't trigger default_offset_commit_callback

[en0]

When using KafkaConsumer there is no way to get a callback when auto commit offset is enabled.

The existing code shows that _maybe_auto_commit_offset_async set's it's own callback that dead-ends and only logs information.

def _commit_offsets_async_on_complete(self, offsets, exception):
        if exception is not None:
            log.warning("Auto offset commit failed for group %s: %s",
                        self.group_id, exception)
            if getattr(exception, 'retriable', False):
                self.next_auto_commit_deadline = min(time.time() + self.config['retry_backoff_ms'] / 1000, self.next_auto_commit_deadline)
        else:
            log.debug("Completed autocommit of offsets %s for group %s",
                      offsets, self.group_id)

    def _maybe_auto_commit_offsets_async(self):
        if self.config['enable_auto_commit']:
            if self.coordinator_unknown():
                self.next_auto_commit_deadline = time.time() + self.config['retry_backoff_ms'] / 1000
            elif time.time() > self.next_auto_commit_deadline:
                self.next_auto_commit_deadline = time.time() + self.auto_commit_interval
                self.commit_offsets_async(self._subscription.all_consumed_offsets(),
                                          self._commit_offsets_async_on_complete)