Implemented basic discriminator map for Attachment API access. Now we can properly create part attachments using a POST operation

src/Serializer/OverrideClassDenormalizer.php

@@ -0,0 +1,61 @@
+<?php
+/*
+ * This file is part of Part-DB (https://github.com/Part-DB/Part-DB-symfony).
+ *
+ *  Copyright (C) 2019 - 2024 Jan Böhmer (https://github.com/jbtronics)
+ *
+ *  This program is free software: you can redistribute it and/or modify
+ *  it under the terms of the GNU Affero General Public License as published
+ *  by the Free Software Foundation, either version 3 of the License, or
+ *  (at your option) any later version.
+ *
+ *  This program is distributed in the hope that it will be useful,
+ *  but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *  GNU Affero General Public License for more details.
+ *
+ *  You should have received a copy of the GNU Affero General Public License
+ *  along with this program.  If not, see <https://www.gnu.org/licenses/>.
+ */
+
+declare(strict_types=1);
+
+
+namespace App\Serializer;
+
+use Symfony\Component\Serializer\Normalizer\DenormalizerAwareInterface;
+use Symfony\Component\Serializer\Normalizer\DenormalizerAwareTrait;
+use Symfony\Component\Serializer\Normalizer\DenormalizerInterface;
+
+/**
+ * The idea of this denormalizer is to allow to override the type of the object created using a certain context key.
+ * This is required to resolve the issue of the serializer/API platform not correctly being able to determine the type
+ * of the "element" properties of the Attachment and Parameter subclasses.
+ */
+class OverrideClassDenormalizer implements DenormalizerInterface, DenormalizerAwareInterface
+{
+    use DenormalizerAwareTrait;
+
+    public const CONTEXT_KEY = '__override_type__';
+
+    public function denormalize(mixed $data, string $type, ?string $format = null, array $context = [])
+    {
+        //Deserialize the data with the overridden type
+        $overrideType = $context[self::CONTEXT_KEY];
+        unset($context[self::CONTEXT_KEY]);
+
+        return $this->denormalizer->denormalize($data, $overrideType, $format, $context);
+    }
+
+    public function supportsDenormalization(mixed $data, string $type, ?string $format = null, array $context = []): bool
+    {
+        return isset($context[self::CONTEXT_KEY]);
+    }
+
+    public function getSupportedTypes(?string $format): array
+    {
+        return [
+            '*' => false,
+        ];
+    }
+}