Camera snapshots and Slack notifications

Configuration
1

I use the Nest component and have my cams up and running with HA. I got the built-in IOS notifications working and have an automation that passes a camera snapshot when motion is detected:

  action:
    service: notify.ios_iphone
    data:
      message: Motion detected on driveway.  Press to view feed.
      data:
        push:
          category: camera
        entity_id: camera.driveway

This produces the following notification:

IMG_4624
IMG_4624332×591 118 KB

I also have a Slack component loaded and notifications working:

  action:
    service: notify.slack
    data_template:
      message: ""
      data: 
        attachments:
        - color: >
            #800040
          title: >
            Garage Door is Open!
          text: |
            Sensor: {{ trigger.to_state.attributes.friendly_name }}
            Time: {{now().strftime("%c")}}

Produces the following channel message:

53%20PM
53%20PM753×95 9.42 KB

My question is, how can I enable camera image snapshots using a Slack automation? I tried several various of the above push camera code with no success. I can’t seem to get the image to pass to Slack.