Send camera image in the notification body

Tags: #<Tag:0x00007fc41a487200>

Hi all,
I want to send a camera snapshot as a “full screen” image. With the code below I get the image but only as a thumbnail (which is very small).

service: notify.mobile_app_my_iphone
data_template:
  message: Snapshot of webcam
  title: Webcam snapshot
  data:
    attachment:
      url: >-
        http://eth0/cgi-bin/api.cgi?cmd=Snap&channel=0&rs=wuuPhfsdfUCeI&user=user&password=pass
      content-type: jpg
      hide-thumbnail: false

I tried all kind of other things but nothing does exactly what I am looking for. Eg.

service: notify.mobile_app_my_iphone
data_template:
  message: Snapshot as photo
  title: Webcam snapshot
  data:
    photo:
      content-type: jpeg
      hide-thumbnail: false
      url: >-
        http://eth0/cgi-bin/api.cgi?cmd=Snap&channel=0&rs=wuuPhfsdfUCeI&user=user&password=mypass

Any hints much appreciated.
BR