title: Elastalert Rules for slack integration (message formatting and Attachments)
body: <p>I'm trying to use message formatting in slack. The Elastalert Testrule.yaml file is partially being parsed. The slack alert shows up with only <code>slack_alert_fields</code> and <code>alert_text</code> fields. I want to send attachments as well in the alerts.
  How to use <code>attachments</code> or create buttons fort slack alerts? </p>
  
  <pre><code>es_host: elasticsearch
  es_port: 9200
  name: Test rule Alert
  type: any
  index: alerts-*
  filter:
  - term:
      alertType.keyword: "New alert created"
  
  alert:
  - "slack"
  
  slack_alert_fields:
  - title: Network Name
    value: networkName
    short: true
  - title: Alert Type
    value: alertType
    short: true
  slack_actions:
  - name: "network url"
    text: "Network URL"
    type: "button"
    value: networkUrl
  
  alert_text: |
              alertData : {0}
  
  alert_text_type: alert_text_only
  alert_text_args: ["alertData"]
  
  attachments: [
      {
          "fallback": "Required plain-text summary of the attachment.",
          "color": "#37964f",
          "pretext": "New alert created",
  
          "title":  alertData.reason ,
          "fields": [
              {
                  "title": "Network Name",
                  "value": networkName,
                  "short" : true
              },
              {
                  "title": "Timestamp",
                  "value": timestamp,
                  "short" : true
              }
              ],
              "actions": [
                  {
                      "name": "network url",
                      "text": "Network URL",
                      "type": "button",
                      "value": networkUrl
                  },
                  {
                      "name": "org_url",
                      "text": "Organization URL",
                      "type": "button",
                      "value":  organizationUrl
  
                  }
  
                  ]
  
      }
      ]
  
  
  slack_webhook_url:
  - "https://hooks.slack.com/xxxxxxxxxxxxxxxxxxxxxxx"
  </code></pre>