message: Removes as_user flag on v2 only
diff: @@ -340,6 +340,14 @@ export class SlackAdapter extends BotAdapter {
  message.user = activity.recipient.id;
  }
  + if (message.icon_url || message.icon_emoji || message.username) {
  + message.as_user = false;
  + }
  +
  + // as_user flag is deprecated on v2
  + if (message.as_user === false && this.options.oauthVersion === 'v2') {
  + delete message.as_user;
  + }
  return message;
  }
  