Main Merge into bug/78 (#80)

* 🔒 Force Single Logout (#77)

Signed-off-by: Luke Tainton <luke@tainton.uk>

* Update assigned-issues-inprogress.yml

Co-authored-by: Luke Tainton <luke@tainton.uk>

app/public/actions/logout.php

@@ -2,7 +2,7 @@
     $PAGE_NAME = "Logging out...";
     require_once __DIR__ . "/../../includes/prereqs.php";
 
+    $access_token = $_SESSION['access_token'];
     session_destroy();
-
-    header('Location: /');
+    $oidc->signOut($access_token, $_ENV['APP_URL']);
 ?>