CDN cache clearing for images

Problem/Motivation

Our CDN stores the image derivatives and when image media focal point changes old image derivatives are still stored on CDN.

I was thinking about clearing the CDN cache on hook_crop_update (purge by url since files don't have any cache tags) but another idea was to change the image urls after focal points for that image change, basically by adding a query parameter to the file URL that depends on focal point values.

I wonder if someone already put a solution for this issue in place.