Add configuration for warranty, payment options, and bookkeeping integration

- Defined constants for warranty months, eligibility window, and service months.
- Enabled automatic invoice forwarding to bookkeeping software with email configuration.
- Integrated payment options for Mollie and PayPal, including API keys and webhook settings.
- Disabled pay on delivery option.

api/v2/post/user_role_assignments.php

@@ -48,7 +48,7 @@ if (isset($post_content['batch_update']) && isset($post_content['user_id']) && i
             if ($existing){
                 //Reactivate existing assignment
                 $stmt = $pdo->prepare('UPDATE user_role_assignments SET is_active = 1, assigned_by = ?, assigned_at = ?, updatedby = ?, updated = ? WHERE rowID = ?');
-                $stmt->execute([$username, $date, $username, $date, $$username]);
+                $stmt->execute([$username, $date, $username, $date, $existing['rowID']]);
             } else {
                 //Create new assignment
                 $stmt = $pdo->prepare('INSERT INTO user_role_assignments (user_id, role_id, is_active, assigned_by, assigned_at, created, createdby) VALUES (?, ?, 1, ?, ?, ?, ?)');