@Override
    public String getContentType() {
        return "application/json";
    }
Using the standard content-type for REST-JSON as a default. For historical context and troubleshooting
related to content-type see https://w.amazon.com/bin/view/AWSSDKsAndTools/JavaSDK/FAQ/TroubleshootingRestJsonIssues/
aws-java-sdk-code-generator/src/main/java/com/amazonaws/codegen/protocol/RestJsonProtocolMetdataProvider.java