chromium/chromeos/components/test/data/onc/ikev2_psk.onc

{ "GUID": "guid",
  "Type": "VPN",
  "Name": "MyIKEv2VPN",
  "VPN": {
    "Type": "IPsec",
    "Host": "some.host.org",
    "IPsec": {
      "AuthenticationType": "PSK",
      "IKEVersion": 2,
      "LocalIdentity": "local-id",
      "PSK": "some_preshared_key",
      "RemoteIdentity": "remote-id",
      "SaveCredentials": true,
    },
  }
}