Auth.auth().createUser(withEmail: usernameField.text!, password: passwordField.text!) { user, error in
            if error == nil {
                if let user = user {
                    let name = "\(self.firstNameField.text!) \(self.surnameField.text!)"
                    //update the currentUser displayName property in Auth.
                    let changeRequest = Auth.auth().currentUser?.createProfileChangeRequest()
                    changeRequest?.displayName = name
                    changeRequest?.commitChanges() { (error) in }
                    //update the people array with the new user
                    Database.database().reference(withPath: "people/\(user.uid)").updateChildValues(
                        ["profile_picture": user.photoURL?.absoluteString ?? "",
                         "full_name": name,
                         "_search_index": ["full_name": user.displayName?.lowercased(),
                                           "reversed_full_name": user.displayName?.components(separatedBy: " ").reversed().joined(separator: "")]])
                    //lastly, sign this new user in.
                    Auth.auth().signIn(withEmail: self.usernameField.text!, password: self.passwordField.text!, completion: { authresult, error in
                        print("Sign in complete, authresult: \(String(describing:authresult)), error: \(String(describing:error))")
                    })
                }
            }
        }
    }