You need to implement producer for user and group related interfaces (UserGroupCallback and UserInfo) and then configure it in beans.xml of the jbpm console web app - by replacing the out of the box producer with your custom one. Here you can find some examples of such producer. Please make sure that your producer and the callback impl is on jbpm console class path (WEB-INF/lib) as callback is a global thing to the app and not scoped to individual kjars.
Can I find somewhere example of a project with classes for replacing authentication in jBPM? because I did not manage to create project with required dependencies and configs? for example I don't know what I should do to get UserGroupInfoProducer interface in project. Sorry if it's not right place for question