UpgradeResult result = strategy.apply(context, pomMap);

            // Should have errors (not just warnings)
            assertTrue(result.errorCount() > 0, "Downgrade should result in errors");
            assertFalse(result.success(), "Downgrade should not be successful");

    If you're using `Call.enqueue()` this update should significantly improve
    request concurrency.

 *  **Fix: Lazily initialize the response cache.** This avoids strict mode
    warnings when initializing OkHttp on Android‘s main thread.

 *  **Fix: Disable ALPN on Android 4.4.** That release of the feature was
    unstable and prone to native crashes in the underlying OpenSSL code.

 * <ul>
 *   <li>{@code [a..a]} : a singleton range
 *   <li>{@code [a..a); (a..a]} : {@linkplain #isEmpty empty} ranges; also valid
 *   <li>{@code (a..a)} : <b>invalid</b>; an exception will be thrown
 * </ul>
 *
 * <h3>Warnings</h3>
 *
 * <ul>
 *   <li>Use immutable value types only, if at all possible. If you must use a mutable type, <b>do
 *       not</b> allow the endpoint instances to mutate after the range is created!

    return construct(e1, e2, e3, e4, e5, e6, e7, e8, e9, e10, e11);
  }

  // These go up to eleven. After that, you just get the varargs form, and
  // whatever warnings might come along with it. :(

  /**
   * Returns an immutable list containing the given elements, in order.
   *
   * <p>The array {@code others} must not be longer than {@code Integer.MAX_VALUE - 12}.
   *

   *
   * @since 7.0
   */
  public static <T extends @Nullable Object> List<T> reverse(List<T> list) {
    if (list instanceof ImmutableList) {
      // Avoid nullness warnings.
      List<?> reversed = ((ImmutableList<?>) list).reverse();
      @SuppressWarnings("unchecked")
      List<T> result = (List<T>) reversed;
      return result;
    } else if (list instanceof ReverseList) {

- API requests to deprecated versions now receive a warning header in the API response, and cause a metric indicating use of a deprecated API to be published:
  - `kubectl` outputs warnings to stderr, and accepts a `--warnings-as-errors` option to treat warnings as fatal errors

## Changes by Kind

### Deprecation

- Added a [warning](https://k8s.io/blog/2020/09/03/warnings/) response when handling requests that set the deprecated `spec.externalID` field for a Node. ([#115944](https://github.com/kubernetes/kubernetes/pull/115944), [@SataQiu](https://github.com/SataQiu)) [SIG Node]
- Added warnings to the Services API. Kubernetes now warns for Services in the case of:

- Kubeadm: improve the strict parsing of user YAML/JSON configuration files. Next to printing warnings for unknown and duplicate fields (current state), also print warnings for fields with incorrect case sensitivity - e.g. `controlPlaneEndpoint` (valid), `ControlPlaneEndpoint` (invalid). Instead of only printing warnings during `init` and `join` also print warnings when downloading the ClusterConfiguration, KubeletConfiguration or KubeProxyConfiguration objects from the cluster....

- Added warnings when creating headless service with set `loadBalancerIP`,`externalIPs` and/or `SessionAffinity`. ([#132214](https://github.com/kubernetes/kubernetes/pull/132214), [@Peac36](https://github.com/Peac36))

- Graduated the `LegacyServiceAccountTokenTracking` feature gate to GA. The usage of auto-generated secret-based service account token now produces warnings, and relevant Secrets are labeled with a last-used timestamp (label key `kubernetes.io/legacy-token-last-used`). ([#117591](https://github.com/kubernetes/kubernetes/pull/117591), [@zshihang](https://github.com/zshihang)) [SIG API Machinery, Auth...