Update process-variables on changing the aggregate

[stephanpelikan]

In some situations there is an update of an aggregate's property which should be synched into Camunda. An example: A workflow waits in an timer-event having an exclusive gateway as a successor. The exclusive gateway's outing flow's FEEL-expressions might need to refer to properties changed during the period of the timer-events. One solution is to add a service-task to update the process-variables based on the aggregate changed meanwhile. It would be better to have a new method <WA> void updateWorkflow(WA workflowAggregate) in ProcessService which does only update process variables based on the given aggregate.