function addSortDefault () {
      if (defaultSort) {
        if (!query.sort) {
          query.sort = [];
        }
        const obj = {};
        obj[defaultSort] = { order: 'asc' };
        obj[defaultSort].missing = '_last';
        query.sort.push(obj);
      }
    }
Adds the sort options to the elasticsearch query
@ignore
@name addSortToQuery
@param {object} query - the elasticsearch query that has been partially built already by buildSessionQuery
@param {object} info - the query params from the client
@param {string} defaultSort - the default sort