public final int port;

  public SlackApi(String clientId, String clientSecret, int port) {
    this.httpClient = new OkHttpClient.Builder()
        .build();
    this.moshi = new Moshi.Builder()
        .add(new SlackJsonAdapters())
        .build();
    this.clientId = clientId;
    this.clientSecret = clientSecret;
    this.port = port;
  }

  /** See https://api.slack.com/docs/oauth. */