Update WorkflowTaskGroup

A container that groups related WorkflowTask instances together, representing a cohesive unit of work. Task groups are created from a WorkflowTaskSchema (via workflowTaskSchema). They are stored in Folders and can have authors and watchers for collaboration. In flowchart workflows, task groups can be nested: childWorkflowTaskGroups contains sub-groups for flowchart nodes, and rootWorkflowTaskGroup points to the parent when this group is part of a larger flowchart. When created from a RequestV2Submission, the requestSubmission field links back to the originating request. Task groups aggregate the outputs from all their tasks via workflowOutputs.