*  Fix: Don't lose HTTP/2 flow control bytes when incoming data races with a stream close. If this
    happened enough then eventually the connection would stall.

 *  Fix: Acknowledge and apply inbound HTTP/2 settings atomically. Previously we had a race where we
    could use new flow control capacity before acknowledging it, causing strict HTTP/2 servers to
    fail the call.

add headers with a fluent builder API.

```java
MockResponse response = new MockResponse()
    .addHeader("Content-Type", "application/json; charset=utf-8")
    .addHeader("Cache-Control", "no-cache")
    .setBody("{}");
```

MockResponse can be used to simulate a slow network. This is useful for
testing timeouts and interactive testing.

```java
response.throttleBody(1024, 1, TimeUnit.SECONDS);

    val headers = headersOf("Cache-Control", "max-age=12", "Pragma", "must-revalidate", "Pragma", "public")
    val cacheControl = parse(headers)
    assertThat(cacheControl.toString()).isEqualTo("max-age=12, public, must-revalidate")
  }

  @Test
  fun parseCacheControlHeaderValueIsRetained() {
    val value = "max-age=12"
    val headers = headersOf("Cache-Control", value)
    val cacheControl = parse(headers)

    val url = "http://host/#\u0080".toHttpUrl()
    assertThat(url.toString()).isEqualTo("http://host/#\u0080")
    assertThat(url.fragment).isEqualTo("\u0080")
    assertThat(url.encodedFragment).isEqualTo("\u0080")
    // Control characters may be stripped!
    assertThat(url.toUri()).isEqualTo(URI("http://host/#"))
  }

  @Test
  fun toUriWithControlCharacters() {
    // Percent-encoded in the path.

  /**
   * Notification that the receiving stream flow control window has changed.
   * [WindowCounter] generally carries the client view of total and acked bytes.
   */
  fun receivingStreamWindowChanged(
    streamId: Int,
    windowCounter: WindowCounter,
    bufferSize: Long,
  )

  /**
   * Notification that the receiving connection flow control window has changed.

            "0000a6d000603617069c012c0300005000100000cde000c04737461720463313072c012c04200010001000" +
            "0003b00049df00112",
        )
          .newBuilder()
          .setHeader("cache-control", "private, max-age=298")
          .build(),
      )
    }

    var result = cachedDns.lookup("google.com")
    assertThat(result).containsExactly(address("157.240.1.18"))

    when {
      name.equals("Cache-Control", ignoreCase = true) -> {
        if (headerValue != null) {
          // Multiple cache-control headers means we can't use the raw value.
          canUseHeaderValue = false
        } else {
          headerValue = value
        }
      }
      name.equals("Pragma", ignoreCase = true) -> {
        // Might specify additional cache-control params. We invalidate just in case.

  }

  companion object {
    /**
     * Cache control request directives that require network validation of responses. Note that such
     * requests may be assisted by the cache via conditional GET requests.
     */
    @JvmField
    val FORCE_NETWORK = commonForceNetwork()

    /**
     * Cache control request directives that uses the cache only, even if the cached response is

    open fun headers(headers: Headers) = commonHeaders(headers)

    /**
     * Sets this request's `Cache-Control` header, replacing any cache control headers already
     * present. If [cacheControl] doesn't define any directives, this clears this request's
     * cache-control headers.
     */
    open fun cacheControl(cacheControl: CacheControl): Builder = commonCacheControl(cacheControl)

  }

fun Request.Builder.commonCacheControl(cacheControl: CacheControl): Request.Builder {
  val value = cacheControl.toString()
  return when {
    value.isEmpty() -> removeHeader("Cache-Control")
    else -> header("Cache-Control", value)
  }
}

fun Request.Builder.commonGet(): Request.Builder = method("GET", null)

fun Request.Builder.commonHead(): Request.Builder = method("HEAD", null)