Unable to perform password authentication

I’ve been following the docs here:

I’m trying to get a token which grants me push access to my repository:
https://hub.docker.com/r/boondocks/device-api/

I’m using these values for the form:

Service = "registry.docker.io";
Realm = "https://auth.docker.io/token";
Scope = "repository:boondocks/device-api:push";

I don’t seem to be able to POST to the specified realm. This is strange because the docs specifically describe this:

POST /token HTTP/1.1
Host: auth.docker.io
Content-Type: application/x-www-form-urlencoded

grant_type=password&username=johndoe&password=A3ddj3w&service=hub.docker.io&client_id=dockerengine&access_type=offline

What am I missing?

Figured it out:

https://gist.github.com/jlhawn/8f218e7c0b14c941c41f

The username / password is sent in a basic authentication header (base64 encoded). Still not sure why the documentation states you can POST to that endpoint.