Accessing custom user data in Drupal 8
In Drupal 7, we can read the current user's custom data by:
global $user;
$user_obj = user_load($user->uid);
print_r($user_obj->data);
... and write by:
global $user;
$user_obj = user_load($user->uid);
user_save($user_obj, array('data' => array('key' => $value)));
Now in Drupal 8, we can read the current user's custom data by: