code: def format_raw_field(key):
      
      subfield = django_settings.WALDUR_CORE.get('ELASTICSEARCH', {}).get('raw_subfield', 'keyword')
      return '%s.%s' % (camel_case_to_underscore(key), subfield)
docs: When ElasticSearch analyzes string, it breaks it into parts.
      In order make query for not-analyzed exact string values, we should use subfield instead.
  
      The index template for Elasticsearch 5.0 has been changed.
      The subfield for string multi-fields has changed from .raw to .keyword
  
      Thus workaround for backward compatibility during migration is required.
      See also: https://github.com/elastic/logstash/blob/v5.4.1/docs/static/breaking-changes.asciidoc