Hello,
[This](https://spaces.at.internet2.edu/display/federation/Configure+IdP+to+release+R+and+S+attributes) is a good doc to follow.
Gluu Server special: You need to configure and modify velocity template instead of shibboleth configuration directly. Such as... "attribute-filter.xml.vm" instead of "attribute-filter.xml" etc.
Then test that with eduGain and/or GENI experiment portal.