how to get current user name in an integrated RPE template

I have several RPE templates to generate documents from DNG, QM and RTC applications.
In order to add log messages in my templates i need to get the current user name (user who is generating the report).
It's okay when using RPE Launcher but with templates integrated to Jazz i can't find how to do it.

Maybe we can use https://server:port/jts/whoami but i don't know how to get the result of this request with a new datasource.

Any ideas ? Thx.