When consuming messages using the plugin, you can access the raw Message and its headers/properties.
When sending messages using the rabbitSend method, it appears from the documentation (http://grails-plugins.github.com/grails-rabbitmq/docs/manual/ref/All%20Classes/rabbitSend.html) that you can only set the exchange name, routing key and message body.
How can these headers/properties be set when sending a message using the rabbitSend method?