feat(mail) : MailConfiguration entity + repository + singleton test

src/Repository/MailConfigurationRepository.php

@@ -0,0 +1,26 @@
+<?php
+
+declare(strict_types=1);
+
+namespace App\Repository;
+
+use App\Entity\MailConfiguration;
+use Doctrine\Bundle\DoctrineBundle\Repository\ServiceEntityRepository;
+use Doctrine\Persistence\ManagerRegistry;
+
+class MailConfigurationRepository extends ServiceEntityRepository
+{
+    public function __construct(ManagerRegistry $registry)
+    {
+        parent::__construct($registry, MailConfiguration::class);
+    }
+
+    public function findSingleton(): ?MailConfiguration
+    {
+        return $this->createQueryBuilder('m')
+            ->setMaxResults(1)
+            ->getQuery()
+            ->getOneOrNullResult()
+        ;
+    }
+}