[export] add a filter and aggregator on activities: filter/group by persons taking part to the activity

src/Bundle/ChillPersonBundle/Export/Helper/LabelPersonHelper.php

@@ -18,6 +18,21 @@ class LabelPersonHelper
 {
     public function __construct(private readonly PersonRepository $personRepository, private readonly PersonRenderInterface $personRender) {}
 
+    public function getLabel(string $key, array $values, string $header): callable
+    {
+        return function (null|int|string $value) use ($header): string {
+            if ('_header' === $value) {
+                return $header;
+            }
+
+            if ('' === $value || null === $value || null === $person = $this->personRepository->find($value)) {
+                return '';
+            }
+
+            return $this->personRender->renderString($person, []);
+        };
+    }
+
     public function getLabelMulti(string $key, array $values, string $header): callable
     {
         return function ($value) use ($header) {