POST /{registration_endpoint_path} request body is JSON

[garethsb]

This note is incorrect:

is-10/APIs/AuthorizationAPI.raml

Lines 166 to 167 in 518b453

	**Note**: Request examples may be rendered as JSON objects, but should be passed in as "application/x-www-form-urlencoded"
	data types, in accordance with [RFC 6749](https://tools.ietf.org/html/rfc6749).

Other request bodies in this API are application/x-www-form-urlencoded but this one isn't.

[lo-simon]

Yes, I think it is incorrect. The content-type should be application/json, we can remove the Note.

[peterbrightwell]

Architecture Review Group review: place on backlog