fix(drupal): Fix PHP 8.2 serialization issue in PdfConversionForm

The readonly constructor-promoted property $conversionService was not
surviving Drupal's AJAX form rebuilds due to PHP 8.2 serialization
behavior. Changed to nullable protected property with lazy loading
via getConversionService() method.

This fixes the "Typed property must not be accessed before
initialization" error when uploading PDF files.

Author: chrisns

cloudformation/scenarios/localgov-drupal/drupal/web/modules/custom/ndx_aws_ai/src/Form/PdfConversionForm.php

@@ -25,15 +25,25 @@ class PdfConversionForm extends FormBase {
    */
   private const MAX_UPLOAD_SIZE_MB = 5;
 
+  /**
+   * The PDF conversion service.
+   *
+   * Note: Not using readonly constructor promotion to avoid PHP 8.2
+   * serialization issues during Drupal AJAX form rebuilds.
+   *
+   * @var \Drupal\ndx_aws_ai\Service\PdfConversionServiceInterface|null
+   */
+  protected ?PdfConversionServiceInterface $conversionService = NULL;
+
   /**
    * Constructs a PdfConversionForm.
    *
-   * @param \Drupal\ndx_aws_ai\Service\PdfConversionServiceInterface $conversionService
+   * @param \Drupal\ndx_aws_ai\Service\PdfConversionServiceInterface|null $conversionService
    *   The PDF conversion service.
    */
-  public function __construct(
-    private readonly PdfConversionServiceInterface $conversionService,
-  ) {}
+  public function __construct(?PdfConversionServiceInterface $conversionService = NULL) {
+    $this->conversionService = $conversionService;
+  }
 
   /**
    * {@inheritdoc}
@@ -44,6 +54,21 @@ public static function create(ContainerInterface $container): static {
     );
   }
 
+  /**
+   * Gets the PDF conversion service.
+   *
+   * Handles re-initialization after form unserialization during AJAX rebuilds.
+   *
+   * @return \Drupal\ndx_aws_ai\Service\PdfConversionServiceInterface
+   *   The conversion service.
+   */
+  protected function getConversionService(): PdfConversionServiceInterface {
+    if ($this->conversionService === NULL) {
+      $this->conversionService = \Drupal::service('ndx_aws_ai.pdf_conversion');
+    }
+    return $this->conversionService;
+  }
+
   /**
    * {@inheritdoc}
    */
@@ -56,7 +81,7 @@ public function getFormId(): string {
    */
   public function buildForm(array $form, FormStateInterface $form_state): array {
     // Check service availability.
-    if (!$this->conversionService->isAvailable()) {
+    if (!$this->getConversionService()->isAvailable()) {
       $form['warning'] = [
         '#type' => 'container',
         '#attributes' => ['class' => ['messages', 'messages--warning']],
@@ -229,7 +254,7 @@ public function submitForm(array &$form, FormStateInterface $form_state): void {
       $fileId = reset($fileIds);
 
       try {
-        $jobId = $this->conversionService->startConversion((int) $fileId);
+        $jobId = $this->getConversionService()->startConversion((int) $fileId);
 
         // Store job ID in session for status checking.
         $this->messenger()->addStatus(