https://api.drupal.org/api/drupal/core%21modules%21user%21src%21Plugin%21EntityReferenceSelection%21UserSelection.php/function/UserSelection%3A%3AdefaultConfiguration/9
function UserSelection::defaultConfiguration | Drupal API
functiondrupalapi
https://api.drupal.org/api/drupal/core%21modules%21user%21src%21Plugin%21EntityReferenceSelection%21UserSelection.php/function/UserSelection%3A%3AvalidateReferenceableNewEntities/8.9.x
function UserSelection::validateReferenceableNewEntities | Drupal API
functiondrupalapi