Issue #2988432 by msankhala, gaurav.kapoor, ravi.shankar, vimal_nadar, joachim, vacho, Berdir, leanderl: Drupal::currentUser() should give sample code to get the current user entity

Issue #2772321 by msankhala, shashikant_chauhan, dhruveshdtripathi, vimal_nadar, joachim: insert() and other public methods with an  param should refer to where to find details on this