client.newCall(request).execute().use {
      assertEquals(204, it.code)
    }

    request =
      Request.Builder()
        .url(endpointUrl)
        .header("Content-Type", "application/xml")
        .put(ErringRequestBody())
        .build()
    assertFailsWith<IOException> {
      client.newCall(request).execute()
    }

    request =
      Request.Builder()
        .url(endpointUrl)
        .head()

```java
class LoggingInterceptor implements Interceptor {
  @Override public Response intercept(Interceptor.Chain chain) throws IOException {
    Request request = chain.request();

    long t1 = System.nanoTime();
    logger.info(String.format("Sending request %s on %s%n%s",
        request.url(), chain.connection(), request.headers()));

    This could have corrupted requests where multiple headers had the same name,
    as in cookies.
 *  Fix: Reject bad characters in the URL hostname. Previously characters like
    `\0` would cause a late crash when building the request.
 *  Fix: Allow interceptors to change the request method.
 *  Fix: Don’t use the request's `User-Agent` or `Proxy-Authorization` when

   * at most once. This is typically used when writing the request body is destructive and it is not
   * possible to recreate the request body after it has been sent.
   *
   * This method returns false unless it is overridden by a subclass.
   *
   * By default OkHttp will attempt to retransmit request bodies when the original request fails
   * due to any of:
   *

```java
OkHttpClient client = new OkHttpClient();

String run(String url) throws IOException {
  Request request = new Request.Builder()
      .url(url)
      .build();

  try (Response response = client.newCall(request).execute()) {
    return response.body().string();
  }
}
```


Post to a Server
----------------

        // spec says that we may repeat the request without modifications. Modern browsers also
        // repeat the request (even non-idempotent ones.)
        if (!client.retryOnConnectionFailure) {
          // The application layer has directed us not to retry the request.
          return null
        }

        val requestBody = userResponse.request.body
        if (requestBody != null && requestBody.isOneShot()) {

 *  New: `Request.Builder.cacheUrlOverride()` customizes the cache key used for a request. This can
    be used to make canonical URLs for the cache that omit insignificant query parameters or other
    irrelevant data.

    This feature may be used with `POST` requests to cache their responses. In such cases the

 * connections should expect repetition of stream IDs.
 *
 * Return true to request cancellation of a pushed stream.  Note that this does not guarantee
 * future frames won't arrive on the stream ID.
 */
interface PushObserver {
  /**
   * Describes the request that the server intends to push a response for.
   *
   * @param streamId server-initiated stream ID: an even number.

 *
 *  1. If the current call already has a connection that can satisfy the request it is used. Using
 *     the same connection for an initial exchange and its follow-ups may improve locality.
 *
 *  2. If there is a connection in the pool that can satisfy the request it is used. Note that it is
 *     possible for shared exchanges to make requests to different host names! See
 *     [RealConnection.isEligible] for details.
 *

 * ⬜️ [Moshi](https://github.com/square/moshi): A modern JSON library for Android and Java.
 * [Ok2Curl](https://github.com/mrmike/Ok2Curl): Convert OkHttp requests into curl logs.
 * [OkHttp AWS Signer](https://github.com/babbel/okhttp-aws-signer): AWS V4 signing algorithm for OkHttp requests
 * [okhttp-digest](https://github.com/rburgst/okhttp-digest): A digest authenticator for OkHttp.