def notify(channel: '#general', text: nil, **opts)
      attachments = text.nil? ? report : []
      text ||= '<http://danger.systems/|Danger> reports'
      @conn.post do |req|
        req.url 'chat.postMessage'
        req.params = {
          token: @api_token,
          channel: channel,
          text: text,
          attachments: attachments.to_json,
          link_names: 1,
          **opts
        }
      end
    end
def notify(channel: '#general', text: nil, **opts)
      attachments = text.nil? ? report : []
      text ||= '<http://danger.systems/|Danger> reports'
      @conn.post do |req|
        req.url 'chat.postMessage'
        req.params = {
          token: @api_token,
          channel: channel,
          text: text,
          attachments: attachments.to_json,
          link_names: 1,
          **opts
        }
      end
    end
notify to Slack

 @param   [String] channel
          It is channel to be notified, defaults to '#general'
 @param   [String] text
          text message posted to slack, defaults to nil.
          if nil, this method post danger reports to slack.
 @param   [Hash] **opts
 @return [void]