[6.x] Add elevated session guards to AssignGroups and AssignRoles actions (#14450)

Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: jasonvarga

src/Actions/AssignGroups.php

@@ -24,6 +24,11 @@ public function authorize($authed, $user)
         return $authed->can('assign user groups');
     }
 
+    public function requiresElevatedSession(): bool
+    {
+        return true;
+    }
+
     public function confirmationText()
     {
         /** @translation */

src/Actions/AssignRoles.php

@@ -24,6 +24,11 @@ public function authorize($authed, $user)
         return $authed->can('assign roles');
     }
 
+    public function requiresElevatedSession(): bool
+    {
+        return true;
+    }
+
     public function confirmationText()
     {
         /** @translation */