Introduce and configure BroadcastMessageConverter used for marshalling to plain text and json.
Ignore all IDEA descriptors.
Latest broadcast controller returns broadcast object, handles no broadcasts found.
Cuts broadcast by id method over to use validation check.
Use media type constants in broadcast controller.
Allows latest message to be identified in multiple media types.
* Adds BroadcastId
* Adds and configures BroadcastIdMessageConverter
* BroadcastController now uses BroadcastId model object
* Step def updated to handle return type as string