docs: def available_providers(request):
      "Adds the list of enabled providers to the context."
      if APPENGINE:
          # Note: AppEngine inequality queries are limited to one property.
          # See https://developers.google.com/appengine/docs/python/datastore/queries#Python_Restrictions_on_queries
          # Users have also noted that the exclusion queries don't work
          # See https://github.com/mlavin/django-all-access/pull/46
          # So this is lazily-filtered in Python
          qs = SimpleLazyObject(lambda: _get_enabled())
      else:
          qs = Provider.objects.filter(consumer_secret__isnull=False, consumer_key__isnull=False)
      return {'allaccess_providers': qs}