task owner / task observer
The possibility to assign a task owner and observers additionally to asignees.
The assignee is responsible for the task, but the observers also get all notifications and are potentially involved.
The creator of a task should automatically be asigned as owner.
Like taiga.io it would be nice to have observers for tasks. We usually have multiple persons that should be informed on changes (comments) to a task but are not the person that is actually executing it.