add user entity

backend/app/Shared/ValueObject/EmailAddress.php

@@ -0,0 +1,40 @@
+<?php
+
+namespace App\Shared\ValueObject;
+
+use InvalidArgumentException;
+
+final readonly class EmailAddress
+{
+    private const string ERROR_MESSAGE = 'Invalid email address:';
+
+    private string $normalized;
+
+    public function __construct(string $email)
+    {
+        $trimmedEmail = trim($email);
+        if (
+            $trimmedEmail === ''
+            || ! str_contains($trimmedEmail, '@')
+        ) {
+            throw new InvalidArgumentException(
+                self::ERROR_MESSAGE." $email",
+            );
+        }
+
+        [$localPart, $domain] = explode('@', $trimmedEmail, 2);
+        $normalizedEmail = $localPart.'@'.mb_strtolower($domain);
+        if (filter_var($normalizedEmail, FILTER_VALIDATE_EMAIL) === false) {
+            throw new InvalidArgumentException(
+                self::ERROR_MESSAGE." $email",
+            );
+        }
+
+        $this->normalized = $normalizedEmail;
+    }
+
+    public function value(): string
+    {
+        return $this->normalized;
+    }
+}