<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def slack_user(request, api_data):
 """ Pipeline for backward compatibility prior to 1.0.0 version. In case if you're willing maintain `slack_user` table. """

    if request.user.is_anonymous:
        return request, api_data

    data = deepcopy(api_data)

    slacker, _ = SlackUser.objects.get_or_create(slacker=request.user)
    slacker.access_token = data.pop('access_token')
    slacker.extras = data
    slacker.save()

    messages.add_message(request, messages.SUCCESS, 'Your account has been successfully updated with '
                                                    'Slack. You can share your messages within your slack '
                                                    'domain.')

    return request, api_data