* string is not human readable, but can be used with classes like [InetAddress] to establish
 * connections.
 *
 * ## Why another URL model?
 *
 * Java includes both [java.net.URL][URL] and [java.net.URI][URI]. We offer a new URL
 * model to address problems that the others don't.
 *
 * ### Different URLs should be different
 *
 * Although they have different content, `java.net.URL` considers the following two URLs

    @Override
    public E element() {
      synchronized (mutex) {
        return delegate().element();
      }
    }

    @Override
    public boolean offer(E e) {
      synchronized (mutex) {
        return delegate().offer(e);
      }
    }

    @Override
    public @Nullable E peek() {
      synchronized (mutex) {
        return delegate().peek();
      }
    }

    @Override
    public E element() {
      synchronized (mutex) {
        return delegate().element();
      }
    }

    @Override
    public boolean offer(E e) {
      synchronized (mutex) {
        return delegate().offer(e);
      }
    }

    @Override
    public @Nullable E peek() {
      synchronized (mutex) {
        return delegate().peek();
      }
    }

    val latch = CountDownLatch(1)
    val responses: BlockingQueue<String?> = SynchronousQueue()
    val authenticator =
      okhttp3.Authenticator { route: Route?, response: Response? ->
        responses.offer(response!!.body.string())
        try {
          latch.await()
        } catch (e: InterruptedException) {
          throw AssertionError()
        }
        response.request
      }

    HTTP/2 server, close all but the first connection.
 *  Fix: Fail the HTTP/2 connection if first frame isn't `SETTINGS`.
 *  Fix: Forbid spaces in header names.
 *  Fix: Don't offer to do gzip if the request is partial.
 *  Fix: MockWebServer is now usable with JUnit 5. That update [broke the rules][junit_5_rules].
 *  New: Support `Expect: 100-continue` as a request header. Callers can use this header to