Engine.

 *  **OkHttp now does cookies.** We've replaced `java.net.CookieHandler` with
    a new interface, `CookieJar` and added our own `Cookie` model class. This
    new cookie follows the latest RFC and supports the same cookie attributes
    as modern web browsers.

 *  **Form and Multipart bodies are now modeled.** We've replaced the opaque
    `FormEncodingBuilder` with the more powerful `FormBody` and

        connectionUser = connectionUser,
        routes = routes,
        requireMultiplexed = planToReplace != null && planToReplace.isReady,
      ) ?: return null

    // If we coalesced our connection, remember the replaced connection's route. That way if the
    // coalesced connection later fails we don't waste a valid route.
    if (planToReplace != null) {
      nextRouteToTry = planToReplace.route
      planToReplace.closeQuietly()

 *  **OkAuthenticator has been replaced with Authenticator.** This new
    authenticator has access to the full incoming response and can respond with
    whichever followup request is appropriate. The `Challenge` class is now a
    top-level class and `Credential` is replaced with a utility class called
    `Credentials`.

 *
 * Neither of the built-in URL models offer direct access to path segments or query parameters.
 * Manually using `StringBuilder` to assemble these components is cumbersome: do '+' characters get
 * silently replaced with spaces? If a query parameter contains a '&', does that get escaped?
 * By offering methods to read and write individual query parameters directly, application
 * developers are saved from the hassles of encoding and decoding.

   * served by the first enqueued response; the second request by the second enqueued response; and
   * so on.
   *
   * @throws ClassCastException if the default dispatcher has been
   * replaced with [setDispatcher][dispatcher].
   */
  fun enqueue(response: MockResponse) = (dispatcher as QueueDispatcher).enqueueResponse(response)

  /**
   * Starts the server on the loopback interface for the given port.

        "A", "a1", "B", "b2", "B", "b3", "Content-Length", "4",
      ),
    )

    // The original 'A' header is retained because the network response doesn't have one.
    // The original 'B' headers are replaced by the network response.
    // The network's 'C' header is added.
    val response2 = get(server.url("/"))
    assertThat(response2.body.string()).isEqualTo("abcd")
    assertThat(response2.headers).isEqualTo(

   APPENDIX: How to apply the Apache License to your work.

      To apply the Apache License to your work, attach the following
      boilerplate notice, with the fields enclosed by brackets "[]"
      replaced with your own identifying information. (Don't include
      the brackets!)  The text should be enclosed in the appropriate
      comment syntax for the file format. We also recommend that a

 * **Route**: address, proxy, socketAddress
 * **TlsVersion**: javaName

#### Renamed Functions

* **Headers.of()**: for symmetry with `listOf()`, `setOf()`, etc., we’ve replaced
  `Headers.of(String...)` with `headersOf(vararg String)`.

#### Extension Functions

We’ve migrated from static functions to extension functions where we think they fit.