Re-generates WebP derivatives for existing media from their originals.
Run this after changing WebP quality config, or to add WebP to media that
predate it. Re-derives from each media's original, so media stored with
keep_original: false (WebP replaced the source) cannot be regenerated and
are skipped with a warning.
Usage
$ mix phx_media_library.regenerate_webp --model MyApp.Catalog.Product
$ mix phx_media_library.regenerate_webp --collection photos --dry-run
Options
--model Only this model type (also needed to read per-collection
WebP overrides; without it the global :webp config is used)
--collection Only this collection
--dry-run Show what would be regenerated