add child creation

backend/app/Controllers/ElementController.php

@@ -3,6 +3,8 @@
 namespace App\Controllers;
 
 use App\Element\Element;
+use App\Element\UseCases\CreateChildElement\CreateChildElement;
+use App\Element\UseCases\CreateChildElement\CreateChildElementRequest;
 use App\Element\UseCases\GetElement\GetElement;
 use App\Element\UseCases\GetElement\GetElementRequest;
 use App\Element\UseCases\UpdateElement\UpdateElement;
@@ -18,6 +20,7 @@ class ElementController
 {
     public function __construct(
         private GetElement $getElement,
+        private CreateChildElement $createChildElement,
         private UpdateElement $updateElement,
         private FileUploader $fileUploader,
     ) {
@@ -55,6 +58,30 @@ class ElementController
         ], 200);
     }
 
+    public function createChild(Request $request, ?int $parentId): JsonResponse
+    {
+        try {
+            $element = $this->createChildElement->execute(
+                new CreateChildElementRequest(
+                    parentElementId: $parentId,
+                    title: $this->stringInput($request, 'title'),
+                )
+            );
+        } catch (BadRequestException $exception) {
+            return new JsonResponse([
+                'error' => $exception->getMessage(),
+            ], 400);
+        } catch (NotFoundException $exception) {
+            return new JsonResponse([
+                'error' => $exception->getMessage(),
+            ], 404);
+        }
+
+        return new JsonResponse([
+            'element' => $this->buildElementPayload($element),
+        ], 201);
+    }
+
     public function update(Request $request): JsonResponse
     {
         $file = $this->uploadedFileInput($request, 'file');