xdmp.userLastLogin(xdmp.user("sylvester"))
  => 
  {
    "userId":"1134406269933351074",
    "lastSuccessfulLogin":"2008-03-19T15:41:08",
    "lastUnsuccessfulLogin":"2008-03-19T15:40:45",
    "numberUnsuccessfulLogins":0,
    "displayLastLogin":true
  }