Add "Logged in" suffix in the HTML head title when users are logged in

This applies for all users - both patrons and library staff.

This assumes that patrons will be logged in as both Drupal users and
with Adgangsplatformen tokens as is currently the case.

DDFLSBP-86

web/modules/custom/dpl_login/dpl_login.module

@@ -93,3 +93,12 @@ function _dpl_login_user_has_been_processed(array $openid_connect_context): bool
   // then we do not attach any information.
   return !$openid_connect_context['is_new'] ?? FALSE;
 }
+
+/**
+ * Implements hook_preprocess_html().
+ */
+function dpl_login_preprocess_html(array &$variables): void {
+  if (\Drupal::currentUser()->isAuthenticated()) {
+    $variables['head_title'][] = t('Logged in', [], ['context' => 'dpl_login']);
+  }
+}