add element child list

backend/app/Element/UseCases/GetElement/GetElement.php

@@ -2,7 +2,6 @@
 
 namespace App\Element\UseCases\GetElement;
 
-use App\Element\Element;
 use App\Element\ElementRepository;
 use App\Exceptions\BadRequestException;
 use App\Exceptions\NotFoundException;
@@ -17,7 +16,7 @@ class GetElement
      * @throws BadRequestException
      * @throws NotFoundException
      */
-    public function execute(GetElementRequest $request): Element
+    public function execute(GetElementRequest $request): GetElementResult
     {
         if ($request->id === null) {
             throw new BadRequestException('id is required');
@@ -28,6 +27,10 @@ class GetElement
             throw new NotFoundException('Element not found');
         }
 
-        return $element;
+        return new GetElementResult(
+            element: $element,
+            childElements: $this->elementRepository
+                ->findByParentElement($element),
+        );
     }
 }

backend/app/Element/UseCases/GetElement/GetElementResult.php

@@ -0,0 +1,30 @@
+<?php
+
+namespace App\Element\UseCases\GetElement;
+
+use App\Element\Element;
+
+class GetElementResult
+{
+    /**
+     * @param Element[] $childElements
+     */
+    public function __construct(
+        private Element $element,
+        private array $childElements,
+    ) {
+    }
+
+    public function getElement(): Element
+    {
+        return $this->element;
+    }
+
+    /**
+     * @return Element[]
+     */
+    public function getChildElements(): array
+    {
+        return $this->childElements;
+    }
+}