Document required MessageBundle adjustments in extended view

[glebfox]

When extending/overriding a view and the MessageBundle is used in this parent view controller, it's required that the messageGroup of the new child view be set to the same value as that of the parent view. Otherwise, messages will be loaded with the messageGroup from a new view, and cannot be found. For example:

@Route(value = "pslock/pessimistic-locks", layout = MainView.class)
@ViewController("pslock_LockInfo.list")
@ViewDescriptor("ts-pessimistic-lock-list-view.xml")
public class TsPessimisticLockListView extends PessimisticLockListView {

    @Override
    public void onInit(InitEvent event) {
        messageBundle.setMessageGroup("io.jmix.pessimisticlockflowui.view.pessimisticlock");
        super.onInit(event);
    }
}