Document HTTP API usage

[treyhunner]

I plan to implement file uploading without Fine Uploader. I will be implementing the upload using ember-cli/jQuery. I will probably end up reverse-engineering the API by reading the tests and code, but it would be nice to eventually have documentation.

[paulmelnikow]

drf-to-s3 implements two separate APIs, one intended for Fine Uploader, and another intended for API clients.

The Fine Uploader interface is pretty well documented, however I'd suggest that you work with the API-client interface instead.

One guy used the API-client version and wrote his own uploader that ran in the browser (see #1), though it reminds me there is a patch for Content-Type that I think needs to come in.

This test that hits the API-client endpoint is the most succinct. There is also a complete xhr example. The first call gets the signed URI, the second call puts the file onto s3, and the third call tells the server the file has been uploaded.

Agreed that some better documentation explaining the sequence of calls would be useful! Certainly would welcome PRs.