observe_media_preview_revision/3
Contribute normalized resource edit settings to the signed preview revision.
Return a list with {Module, Settings} prepended to the accumulator. Contributions
must be stable terms and include every persistent setting affecting image edits.
The core hashes the sorted contributions; they do not enter the rendering pipeline.
Called when generating preview URLs and checking preview retention. This must be
inexpensive and must not download or inspect source files. The original image
option bypasses revision tracking. #media_preview_revision.id is the resource id.
Type: foldl.