[1,2,3,4]
Details for user #1:
* Name: Alice
* Age: 30
* Groups: [{"id": 1, "name": "admin"}]
Details for user #2:
* Name: Bob
* Age: N/A
* No groups
Details for user #3:
* Name: Charlie
* Age: 25
* Groups: []
Details for user #4:
* Name: Darlene
* Age: 40
* Groups: [{"id": 2, "name": "groupA"},{"id": 3, "name": "groupB"}]