Difficulty decoupling PersonViewController from Firebase calls

[kelvinlauKL]

This demo tries to isolate the Firebase calls in the Server namespace, however a Firebase call is done in PersonViewController:

override func viewDidLoad() {
  super.viewDidLoad()

  let personRef = FIRDatabase.database().reference().child("people")
  personRef.observe(.childAdded, with: { snapshot in
    guard let personDict = snapshot.value as? [String: Any] else { return print("couldn't cast") }
    let person = Person(dictionary: personDict)
    self.people.append(person)
    self.tableView.insertRows(at: [IndexPath(row: self.people.count - 1, section: 0)], with: .automatic)
  })
}

Ideally, you'd want this call to reside in the Server enum.