* License as published by the Free Software Foundation; either
 * version 2.1 of the License, or (at your option) any later version.
 *
 * This library is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * Lesser General Public License for more details.
 *

 * `MODERN_TLS` is a secure configuration that connects to modern HTTPS servers.
 * `COMPATIBLE_TLS` is a secure configuration that connects to secure–but not current–HTTPS servers.
 * `CLEARTEXT` is an insecure configuration that is used for `http://` URLs.

It could be just one or two lines of code, like:

```Python
callback_url = "https://example.com/api/v1/invoices/events/"
httpx.post(callback_url, json={"description": "Invoice paid", "paid": True})
```

But possibly the most important part of the callback is making sure that your API user (the external developer) implements the *external API* correctly, according to the data that *your API* is going to send in the request body of the callback, etc.

But it's possible to customize it, you can set a specific CDN, or serve the files yourself.

## Custom CDN for JavaScript and CSS { #custom-cdn-for-javascript-and-css }

   * Returns a fixed-size list backed by the specified array, similar to {@link
   * Arrays#asList(Object[])}. The list supports {@link List#set(int, Object)}, but any attempt to
   * set a value to {@code null} will result in a {@link NullPointerException}.
   *
   * <p>The returned list maintains the values, but not the identities, of {@code Character} objects
   * written to or read from it. For example, whether {@code list.get(0) == list.get(0)} is true for

    if (returnValue == null) {
      Assert.assertTrue(
          factory + " returns null but it's not annotated with @Nullable", isNullable(factory));
    }
    return returnValue;
  }

  /**
   * Thrown if the test tries to invoke a constructor or static factory method but failed because
   * the dummy value of a constructor or method parameter is unknown.
   */
  @VisibleForTesting

 *
 * This class supports [asynchronous canceling][cancel]. This is intended to have the smallest
 * blast radius possible. If an HTTP/2 stream is active, canceling will cancel that stream but not
 * the other streams sharing its connection. But if the TLS handshake is still in progress then
 * canceling may break the entire connection.
 */
class RealCall(
  val client: OkHttpClient,

    assertThat(startupTimes).hasSize(2);
    assertThat(startupTimes.get(a)).isAtLeast(150);
    // Service b startup takes at least 353 millis, but starting the timer is delayed by at least
    // 150 milliseconds. so in a perfect world the timing would be 353-150=203ms, but since either
    // of our sleep calls can be arbitrarily delayed we should just assert that there is a time
    // recorded.

// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// This program is distributed in the hope that it will be useful
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU Affero General Public License for more details.
//

   * method propagate untouched, just as we'd typically let it do for a non-reflective call.
   * However, we can't usually write {@code throw t;} when {@code t} has a static type of {@link
   * Throwable}. But we <i>can</i> write {@code sneakyThrow(t);}.
   *
   * <p>We sometimes also use {@code sneakyThrow} for testing how our code responds to
   * sneaky checked exception.
   *