long running rest requests

[rizen]

This could be a good way to handle things like the image uploads that are pending processing, or ving jobs.

POST /api/v1/whatever

return: 202 Accepted Location: /api/v1/whatever/status/99

---

GET /api/v1/whatever/status/99

return: 303 See Other Location: /api/v1/whatever/99 { secondsToComplete: 33, percentComplete: 45 }