SWITCHYARD-1484 introduced the ability to specify an implementation of a UserGroupCallback on our BPM component.

The class must implement this interface:
org.kie.internal.task.api.UserGroupCallback

An example of the userGroupCallback XML element is below:

<implementation.bpm>
    <userGroupCallback class="com.example.MyUserGroupCallbackImpl">
        <properties>
            <property name="foo" value="bar"/>
        </properties>
    </userGroupCallback>
</implementation.bpm>

The element itself is optional, as is the class attribute, and the runtime will default to a org.switchyard.component.bpm.runtime.BPMUserGroupCallback.
The properties element is optional, as are it's children (and is our standard properties that we support elsewhere).

Schema diff is here: http://goo.gl/uVdQE