additional improvements for Kotlin users. In this alpha we're excited to skip-the-builder for
requests and remove a common source of non-null assertions (`!!`) on the response body.

The alpha releases in the 5.0.0 series have production-quality code and an unstable API. We expect
to make changes to the APIs introduced in 5.0.0-alpha.X. These releases are safe for production use
and 'alpha' strictly signals that we're still experimenting with some new APIs. If you're eager for

   * ```
   * Content-Type: text/html
   * Content-Length: 050
   * ```
   *
   * Applications that require semantically equal headers should convert them into a canonical form
   * before comparing them for equality.
   */
  override fun equals(other: Any?): Boolean = commonEquals(other)

  override fun hashCode(): Int = commonHashCode()

  /**

    fun Response.hasVaryAll(): Boolean = "*" in headers.varyFields()

    /**
     * Returns the names of the request headers that need to be checked for equality when caching.
     */
    private fun Headers.varyFields(): Set<String> {
      var result: MutableSet<String>? = null
      for (i in 0 until size) {
        if (!"Vary".equals(name(i), ignoreCase = true)) {