Add Thumbnail to clip metadata

[vekexasia]

Describe what you are trying to accomplish and why in non technical terms
When downloading the video i'd like to have the thumbnail metadata to be set to the event snapshot so that i can instantaneously see the "event" highlight and eventually play the whole clip.

Describe the solution you'd like
Apparently adding the thumbnail is pretty straightforward with ffmpeg. https://stackoverflow.com/questions/54717175/how-do-i-add-a-custom-thumbnail-to-a-mp4-file-using-ffmpeg

Additional context
I send out both event snapshots and clips via telegram for instant notification on my phone but I'd like to send the vid only with the thumbnail properly set :).