add set layout api

backend/tests/Fakes/FakeElementRepository.php

@@ -39,6 +39,20 @@ class FakeElementRepository implements ElementRepository
         return $element === null ? null : $this->copy($element);
     }
 
+    public function findBySet(Set $set): array
+    {
+        $elements = array_filter(
+            $this->elements,
+            function (Element $element) use ($set): bool {
+                return $element->getSet()->getId() === $set->getId();
+            },
+        );
+
+        return array_map(function (Element $element): Element {
+            return $this->copy($element);
+        }, array_values($elements));
+    }
+
     public function findTopLevelBySet(Set $set): array
     {
         $elements = array_filter(

backend/tests/Fakes/FakeSetRepository.php

@@ -26,6 +26,13 @@ class FakeSetRepository implements SetRepository
         return $this->copy($set);
     }
 
+    public function find(int $id): ?Set
+    {
+        $set = $this->sets[$id] ?? null;
+
+        return $set === null ? null : $this->copy($set);
+    }
+
     public function all(): array
     {
         $sets = array_values($this->sets);

backend/tests/Feature/Set/GetSetLayoutEndpointTest.php

@@ -17,6 +17,7 @@ use App\User\UserRepository;
 use DateTimeImmutable;
 use DateTimeZone;
 use Illuminate\Foundation\Testing\RefreshDatabase;
+use Illuminate\Testing\TestResponse;
 use Tests\TestCase;
 
 class GetSetLayoutEndpointTest extends TestCase
@@ -160,7 +161,7 @@ class GetSetLayoutEndpointTest extends TestCase
         ));
     }
 
-    private function credentialedGet(string $uri): \Illuminate\Testing\TestResponse
+    private function credentialedGet(string $uri): TestResponse
     {
         return $this->withCredentials()
             ->withUnencryptedCookie(

backend/tests/Unit/Set/UseCases/GetSetLayoutTest.php

@@ -5,6 +5,7 @@ namespace Tests\Unit\Set\UseCases;
 use App\Element\CreateElementDto;
 use App\Exceptions\NotFoundException;
 use App\Set\CreateSetDto;
+use App\Set\UseCases\GetSetLayout\ElementLayoutNode;
 use App\Set\UseCases\GetSetLayout\GetSetLayout;
 use App\Shared\ValueObject\EmailAddress;
 use App\User\User;
@@ -124,7 +125,7 @@ class GetSetLayoutTest extends TestCase
     }
 
     /**
-     * @param list<\App\Set\UseCases\GetSetLayout\ElementLayoutNode> $nodes
+     * @param list<ElementLayoutNode> $nodes
      * @return list<string>
      */
     private function nodeNames(array $nodes): array