User uploads are inserted into S3 object store

[colelawrence]

This is the tracking feature for #4

I'm creating the issue here to collect thoughts and discoveries as this feature is developed.

I ran into some simple problems trying to upload directly to the server, where Cloudflare's CDN (providing free SSL) prevents uploads of more than 100MB. So, I disabled Cloudflare's DNS to see how it would upload, and got mixed results with a 200MB MP4 file (pausing and resuming or event timing out once).

Given that mixed result, I think it would be wise to upload directly to our S3 implementation (testing with Minio) using pre-signed post urls.

This would also help pull us in the direction of relying on the distributed properties of an existing CDN, rather than attempting to optimize our own traffic.