code: function pruneHeaders(requestHeaders) {
    const headers = Object.assign({}, requestHeaders);
  
    delete headers.trackingid;
    delete headers.authorization;
  
    return headers;
  }
docs: Remove headers that are unique for each request
  from the given headers object. This ensures
  that certain headers do not "bust" the hash.
  @param {Object} requestHeaders
  @returns {Object} a new, pruned headers object