If you wish to debug a RESTClient call, just add the following configuration to your logging section: [Coming from Grails, this should go in your logging section]. (This configuration setting targets the Http Client that is used within RestClient)
debug 'org.apache.http.headers', 'org.apache.http.wire'
The finding of this was <a href="https://blog.techstacks.com/2009/12/configuring-wire-logging-in-groovy-httpbuilder.html">found by Chris Mahns</a>.