DX: fix phpstan issues

src/Bundle/ChillCalendarBundle/Entity/Calendar.php

@@ -29,6 +29,7 @@ use DateTimeImmutable;
 use Doctrine\Common\Collections\ArrayCollection;
 use Doctrine\Common\Collections\Collection;
 use Doctrine\Common\Collections\Criteria;
+use Doctrine\Common\Collections\ReadableCollection;
 use Doctrine\ORM\Mapping as ORM;
 use LogicException;
 use Symfony\Component\Serializer\Annotation as Serializer;
@@ -507,10 +508,10 @@ class Calendar implements TrackCreationInterface, TrackUpdateInterface, HasCente
     }
 
     /**
-     * @return Collection|User[]
+     * @return ReadableCollection<(int|string), User>
      * @Serializer\Groups({"calendar:read", "read"})
      */
-    public function getUsers(): Collection
+    public function getUsers(): ReadableCollection
     {
         return $this->getInvites()->map(static function (Invite $i) {
             return $i->getUser();