code: function redirect(ctx, url, status) {
    if (ctx.accepts('html', 'json') === 'json') {
      ctx.set('Location', url);
      ctx.status = 401;
      ctx.body = {
        error: '401 Unauthorized'
      };
      return;
    }
    return ctx.redirect(url, status);
  }
docs: Send redirect response.
  
  @param  {Context} ctx
  @param  {String} url, redirect URL
  @param  {Number|String} status, response status code, default is `302`
  
  @api public