feat(user): add DTO/Mapper

see: #30

src/Service/User/UserDTO.php

@@ -0,0 +1,49 @@
+<?php
+
+namespace App\Service\User;
+
+final class UserDTO
+{
+    public function __construct(
+        private string $email = '',
+        private ?string $slug = null,
+        private array $projects = [],
+    ) {
+    }
+
+    public function getSlug(): ?string
+    {
+        return $this->slug;
+    }
+
+    public function setSlug(string $slug): self
+    {
+        $this->slug = $slug;
+
+        return $this;
+    }
+
+    public function getEmail(): ?string
+    {
+        return $this->email;
+    }
+
+    public function setEmail(string $email): self
+    {
+        $this->email = $email;
+
+        return $this;
+    }
+
+    public function getProjects(): array
+    {
+        return $this->projects;
+    }
+
+    public function setProjects(array $projects): self
+    {
+        $this->projects = $projects;
+
+        return $this;
+    }
+}

src/Service/User/UserMapper.php

@@ -0,0 +1,29 @@
+<?php
+
+namespace App\Service\User;
+
+use App\Entity\User;
+use Symfony\Component\Serializer\Encoder\JsonEncoder;
+use Symfony\Component\Serializer\Normalizer\ObjectNormalizer;
+use Symfony\Component\Serializer\Serializer;
+
+final class UserMapper
+{
+    /** @throws ExceptionInterface */
+    public static function fromEntityToJson(User $user): mixed
+    {
+        $dto = self::fromEntityToDTO($user);
+        $serializer = new Serializer([new ObjectNormalizer()]);
+
+        return $serializer->normalize($dto, JsonEncoder::FORMAT);
+    }
+
+    public static function fromEntityToDTO(User $user): UserDTO
+    {
+        return new UserDTO(
+            $user->getEmail(),
+            $user->getSlug(),
+            // UserHelper::getCategoriesArrayFromUser($user)
+        );
+    }
+}