We can now get users groups from Redmine api. For this, when retrieving Users, add "groups" to INCLUDE
cf:
transport.getObjectsList(User.class, new BasicNameValuePair(

•           "include", "memberships"));
  

•           "include", "memberships,groups"));
  

  then we can make available the "GetGroups" method in User.java.

I have made the modification successfully, will try to pull request ASAP