*
   * @param method defaults to "GET" if [body] is null, and "POST" otherwise.
   */
  constructor(
    url: HttpUrl,
    headers: Headers = headersOf(),
    // '\u0000' is a sentinel value that'll choose based on what the body is:
    method: String = "\u0000",
    body: RequestBody? = null,
  ) : this(
    Builder()
      .url(url)
      .headers(headers)
      .method(
        when {