Add Date Created and Date Updated to Users collection

### Describe the Improvement

It's useful in many cases to have Date Created and Date Updated for Users collection.

The issue does not name a file, test, or entry point. Start by locating where the Users collection is defined and how its fields are exposed, then clarify the expected date fields and their behavior; done means the Users collection provides both creation and update dates consistently.

Written by the indexing model from the issue text.