Fix to ptif image conversion and adding a date-based bulk convert task - #134

Looking great! Just one suggested change.

Suggested change makes sense to me; but then would that reasoning also apply to the other tasks in this file, or at least some of them? (convert_images, convert_images_by_type, convert_images_by_colorspace) Although I suppose those were probably written with the intent to include images that had never yet been converted, whereas in this particular context of fixing the flat TIFFs we only need to target resources that have converted_content? Still the inconsistency between otherwise basically identical tasks feels a bit weird.

Suggested change makes sense to me; but then would that reasoning also apply to the other tasks in this file, or at least some of them? (convert_images, convert_images_by_type, convert_images_by_colorspace) Although I suppose those were probably written with the intent to include images that had never yet been converted, whereas in this particular context of fixing the flat TIFFs we only need to target resources that have converted_content? Still the inconsistency between otherwise basically identical tasks feels a bit weird.

Right, exactly. And moreover, we are targeting conversion date for these—which relies on a conversion—whereas we are targeting properties of the source image for the others (whether or not it is an image, MIME type, and EXIF colorspace). Maybe a more accurate name for this new task is "reconvert" but IMO it's clear enough as-is.