Heroku Changelog Platform API has a new format for referencing resources

Change effective on 17 October 2013

We’re changing the way resources are identified in requests to the Platform API: Instead of a nested object containing either the resource id (eg: "user":{"id":"01234..."}) or a human-friendly identifier (eg: "user":{"email":"username@example.com"}), you now have to supply a simple attribute containing either the id or the friendly identifier: "user":"01234..." or "user":"username@example.com".

The previous format will continue to work until Nov 4th. For more info please refer to this list of specific endpoints that are affected.