code: function writeToFileStream(fileStream, filePath) {
    return new Promise((resolve, reject) => {
      const writerStream = fs.createWriteStream(filePath)
        .on('finish', () => resolve(filePath))
        .on('error', err => reject(err));
      fileStream.pipe(writerStream);
    });
  }
docs: Write a stream to a file
  @param {stream} fileStream the stream payload
  @param {string} filePath path and filename: where store the file
  @returns {Promise} resolve with the filePath when the stream finish