I use Firestore JavaScript v9. I have a data structure of items with deeply nested tasks, like this:

• item A
  • task1
    • task1.1
  • task2
• item B
  • task1
  • task2
    • task2.1
      • task2.1.1

Every Task has an endDate Timestamp and a subcollection "subTasks".

How can I query the max / latest endDate of all subTasks within an item?