How to change Task's Owner/PotentialOwners after Task creation in jBPM5

Issue

• If the task is unclaimed then user B can correctly perform any task operation, if the task is claimed (such as by user A), the business administrator (user B) cannot perform any task operations.
• Users and groups are assigned to the human task when the process is started. Now when the process engine arrives at the human task node, the process variables are copied to ActorID and GroupID parameters using expressions.
  • Now the admin wants to remove existing users and add new ones before that task can be claimed and started.
  • admin also wants to remove some existing groups and add new ones before task can be claimed and started.