If a user accesses a saved article while migration is taking place, it should fall through to the normal Image manager logic. As a result, if a user is offline, saved pages images will be broken until the migration is complete.

Do not worry about notifying the user about migration in this patch, UX needs will be evaluated later on and we can add user notifications if needed.

• Add logic to delete images associated with a page when it is deleted
• Add background task to migrate images from saved pages into SDWebImage
• Start background task on launch