add initial admin

backend/app/User/UseCases/EnsureInitialAdmin/EnsureInitialAdmin.php

@@ -0,0 +1,31 @@
+<?php
+
+namespace App\User\UseCases\EnsureInitialAdmin;
+
+use App\Auth\PasswordHasher;
+use App\Shared\ValueObject\EmailAddress;
+use App\User\CreateUserDto;
+use App\User\UserRepository;
+
+class EnsureInitialAdmin
+{
+    public function __construct(
+        private UserRepository $userRepository,
+        private PasswordHasher $passwordHasher,
+    ) {
+    }
+
+    public function execute(EnsureInitialAdminRequest $request): void
+    {
+        $email = new EmailAddress($request->email);
+        $existingUser = $this->userRepository->findByEmail($email);
+        if ($existingUser !== null) {
+            return;
+        }
+
+        $this->userRepository->create(new CreateUserDto(
+            email: $email,
+            passwordHash: $this->passwordHasher->hash($request->password),
+        ));
+    }
+}