add element endpoint

backend/app/Controllers/ElementController.php

@@ -0,0 +1,25 @@
+<?php
+
+namespace App\Controllers;
+
+use App\Element\ElementRepository;
+use Illuminate\Http\JsonResponse;
+
+class ElementController
+{
+    public function __construct(private ElementRepository $elementRepository)
+    {
+    }
+
+    public function show(int $id): JsonResponse
+    {
+        $element = $this->elementRepository->find($id);
+
+        return new JsonResponse([
+            'element' => [
+                'id' => $element->getId(),
+                'title' => $element->getTitle(),
+            ],
+        ], 200);
+    }
+}