* Returns true if none of the Vary headers have changed between [cachedRequest] and
     * [newRequest].
     */
    fun varyMatches(
      cachedResponse: Response,
      cachedRequest: Headers,
      newRequest: Request,
    ): Boolean =
      cachedResponse.headers.varyFields().none {
        cachedRequest.values(it) != newRequest.headers(it)
      }