Allow assigning groups in mapperScript using JavaScript

I am attempting to complete Okta integration using the saml2-authentication add-on on and the nuxeo-usermapper service. The problem is that there is no way to assign groups from the mapperScript when using JavaScript; there is no context object for the group assignment (check out org.nuxeo.usermapper.extension.NashornUserMapper.java). I am following the readme here:

https://github.com/nuxeo/nuxeo/blob/master/nuxeo-services/nuxeo-usermapper/README.md

Without group assignment, the js mapperScript is actually not useful, unless the groups are manually assigned after the user has connected at least once, because you end up with a user who has no groups.

NB: I am assuming that I will be able to complete the group assignment using Groovy; even though there is no context object for groups, I can create one.