Refactor FormSubmissionDataFactory to use TestHelpers trait

- Move FormSubmissionDataFactory methods into TestHelpers trait
- Update import statements across multiple test files
- Remove standalone FormSubmissionDataFactory class
- Simplify form submission data generation in tests
- Add documentation for new generateFormSubmissionData method

api/tests/Feature/Forms/CustomSmtpTest.php

@@ -1,7 +1,6 @@
 <?php
 
 use App\Notifications\Forms\FormEmailNotification;
-use Tests\Helpers\FormSubmissionDataFactory;
 use Illuminate\Notifications\AnonymousNotifiable;
 use Illuminate\Support\Facades\Notification;
 
@@ -40,7 +39,7 @@ it('send email with custom SMTP settings', function () {
         'reply_to' => 'reply@example.com',
     ]);
 
-    $formData = FormSubmissionDataFactory::generateSubmissionData($form);
+    $formData = $this->generateFormSubmissionData($form);
 
     Notification::fake();