feat: show room prices in room assignment form field

src/Form/DataTransformer/RoomSelectionToIdTransformer.php

@@ -0,0 +1,79 @@
+<?php
+
+declare(strict_types=1);
+
+namespace App\Form\DataTransformer;
+
+use App\Form\Model\RoomSelectionDto;
+use Symfony\Component\Form\DataTransformerInterface;
+use Symfony\Component\Form\Exception\TransformationFailedException;
+
+/**
+ * Transforms between RoomSelectionDto objects and integer room IDs.
+ *
+ * This transformer enables using RoomSelectionDto objects as choices while
+ * binding integer IDs to the model. This allows the template to access
+ * the full object (including price) via choiceData while the form binds
+ * the scalar ID to the participant's assignedRoomId property.
+ *
+ * @implements DataTransformerInterface<int|null, RoomSelectionDto|null>
+ */
+class RoomSelectionToIdTransformer implements DataTransformerInterface
+{
+    /**
+     * @param RoomSelectionDto[] $roomSelections Available room selections for reverse lookup
+     */
+    public function __construct(
+        private readonly array $roomSelections,
+    ) {
+    }
+
+    /**
+     * Transforms an integer room ID to a RoomSelectionDto for form display.
+     *
+     * @param int|null $value The room ID from the model
+     *
+     * @return RoomSelectionDto|null The matching RoomSelectionDto or null
+     */
+    public function transform(mixed $value): ?RoomSelectionDto
+    {
+        if (null === $value) {
+            return null;
+        }
+
+        foreach ($this->roomSelections as $roomSelection) {
+            if ($roomSelection->id === $value) {
+                return $roomSelection;
+            }
+        }
+
+        return null;
+    }
+
+    /**
+     * Transforms a RoomSelectionDto back to an integer room ID for the model.
+     *
+     * @param RoomSelectionDto|null $value The selected RoomSelectionDto from the form
+     *
+     * @return int|null The room ID or null
+     *
+     * @throws TransformationFailedException If an unexpected value type is received
+     */
+    public function reverseTransform(mixed $value): ?int
+    {
+        if (null === $value) {
+            return null;
+        }
+
+        if ($value instanceof RoomSelectionDto) {
+            return $value->id;
+        }
+
+        // Handle case where form submits scalar ID directly
+        if (is_int($value) || is_string($value)) {
+            return (int) $value;
+        }
+
+        throw new TransformationFailedException(sprintf('Expected RoomSelectionDto, int, or null, got %s', get_debug_type($value)));
+    }
+}