Files to be reviewed

Not performance at all. And really, these aren't magic numbers, per se, I'm probably just being a bit overly aggressive. If you put it into settings, then if the multipart threshold or whatever change, then you know the place to look for the change. It also lets you easily have different settings in develop vs staging etc, in case that's ever useful. The normal reason for using settings.

Proper magic numbers would have been using 1024 ** 2 * 250 actually in the code later on, or worse 262144000. Slightly better that what's above would be a setting for the multipart_threshold_mb = 500 in the settings, and multipart_threshold here being 1024 ** 2 * mutlipart_threshold_mb or what-have-you.

This is fairly minor.