code: function apply(data, mapping) {
    const mp = mapping.hasOwnProperty('field') ? singleToMulti(mapping) : mapping;
    data.records
      .filter(rcd => mp.mapping.hasOwnProperty(rcd[mp.key]))
      .forEach(rcd => {
        mp.fields.forEach((fd, i) => {
          rcd[fd.key] = mp.mapping[rcd[mp.key]][i];
        });
      });
    data.fields =  _(data.fields)
      .concat(mp.fields)
      .uniqBy('key')
      .value();
  }
docs: Apply mapping to the data (in-place)
  @param {object} data - datatable JSON
  @param {object} mapping - mapping JSON
  @return {undefined} undefined