.add(new SlackJsonAdapters())
        .build();
    this.clientId = clientId;
    this.clientSecret = clientSecret;
    this.port = port;
  }

  /** See https://api.slack.com/docs/oauth. */
  public HttpUrl authorizeUrl(String scopes, HttpUrl redirectUrl, ByteString state, String team) {
    HttpUrl.Builder builder = baseUrl.newBuilder("/oauth/authorize")
        .addQueryParameter("client_id", clientId)

        .setType(MultipartBody.FORM)
        .addFormDataPart("title", "Square Logo")
        .addFormDataPart("image", "logo-square.png",
            RequestBody.create(
                new File("docs/images/logo-square.png"),
                MEDIA_TYPE_PNG))
        .build();

    Request request = new Request.Builder()
        .header("Authorization", "Client-ID " + IMGUR_CLIENT_ID)