Add PdfSignedMessage and its serializer

Added a new class, PdfSignedMessage, to handle received signed PDF messages. Also, added a serializer for this class, PdfSignedMessageSerializer, for use with messaging. Furthermore, comment documentation has been added to RequestPdfSignMessage and its serializer for better clarity. Updated unit tests are also included.

src/Bundle/ChillDocStoreBundle/Service/Signature/Driver/BaseSigner/PdfSignedMessageSerializer.php

@@ -0,0 +1,66 @@
+<?php
+
+declare(strict_types=1);
+
+/*
+ * Chill is a software for social workers
+ *
+ * For the full copyright and license information, please view
+ * the LICENSE file that was distributed with this source code.
+ */
+
+namespace Chill\DocStoreBundle\Service\Signature\Driver\BaseSigner;
+
+use Symfony\Component\Messenger\Envelope;
+use Symfony\Component\Messenger\Exception\MessageDecodingFailedException;
+use Symfony\Component\Messenger\Transport\Serialization\SerializerInterface;
+
+/**
+ * Decode (and requeue) @see{PdfSignedMessage}, which comes from an external producer.
+ */
+final readonly class PdfSignedMessageSerializer implements SerializerInterface
+{
+    public function decode(array $encodedEnvelope): Envelope
+    {
+        $body = $encodedEnvelope['body'];
+
+        try {
+            $decoded = json_decode($body, true, 512, JSON_THROW_ON_ERROR);
+        } catch (\JsonException $e) {
+            throw new MessageDecodingFailedException('Could not deserialize message', previous: $e);
+        }
+
+        if (!array_key_exists('signatureId', $decoded) || !array_key_exists('content', $decoded)) {
+            throw new MessageDecodingFailedException('Could not find expected keys: signatureId or content');
+        }
+
+        $content = base64_decode($decoded['content'], true);
+
+        if (false === $content) {
+            throw new MessageDecodingFailedException('Invalid character found in the base64 encoded content');
+        }
+
+        $message = new PdfSignedMessage($decoded['signatureId'], $content);
+
+        return new Envelope($message);
+    }
+
+    public function encode(Envelope $envelope): array
+    {
+        $message = $envelope->getMessage();
+
+        if (!$message instanceof PdfSignedMessage) {
+            throw new MessageDecodingFailedException('Expected a PdfSignedMessage');
+        }
+
+        $data = [
+            'signatureId' => $message->signatureId,
+            'content' => base64_encode($message->content),
+        ];
+
+        return [
+            'body' => json_encode($data, JSON_THROW_ON_ERROR),
+            'headers' => [],
+        ];
+    }
+}