final void addUserToGroup(Message message) {
        String[] tokens = message.message.split(",");
        String user = tokens[0];
        String group = tokens[1];

        if(groupData.containsKey(group)) {
            GroupRecord gr = groupData.get(group);
            if(gr.owner.equals(message.token.getSubject())) {
                if(userData.containsKey(user)) {
                    UserRecord ur = userData.get(user);
                    ur.groups.add(group);
                    gr.members.add(user);
                    message.message = "user added to group.";
                    message.success = true;
                } else {
                    message.message = "user does not exist.";
                    message.success = false;
                }
            } else {
                message.message = "only the group owner may add members.";
                message.success = false;
            }
        } else {
            message.message = "group does not exist.";
            message.success = false;
        }
    }