feat: fold purchase and promo voucher fields into one code field

tests/Service/VoucherCodeClassifierTest.php

@@ -0,0 +1,58 @@
+<?php
+
+declare(strict_types=1);
+
+namespace App\Tests\Service;
+
+use App\Enum\VoucherCodeKind;
+use App\Service\VoucherCodeClassifier;
+use PHPUnit\Framework\Attributes\DataProvider;
+use PHPUnit\Framework\TestCase;
+
+class VoucherCodeClassifierTest extends TestCase
+{
+    private VoucherCodeClassifier $classifier;
+
+    protected function setUp(): void
+    {
+        $this->classifier = new VoucherCodeClassifier(['lw0705' => '2027-04-30']);
+    }
+
+    /**
+     * @return iterable<string, array{string, VoucherCodeKind}>
+     */
+    public static function codes(): iterable
+    {
+        yield 'prefixed promo' => ['R-SOMMER26', VoucherCodeKind::Promo];
+        yield 'prefixed promo in lowercase' => ['r-sommer26', VoucherCodeKind::Promo];
+        yield 'legacy promo, matched case-insensitively' => ['Lw0705', VoucherCodeKind::Promo];
+        yield 'purchase code' => ['1F7V6PADRZ', VoucherCodeKind::Purchase];
+        yield 'purchase code in lowercase' => ['1f7v6padrz', VoucherCodeKind::Purchase];
+        yield 'surrounding whitespace' => ['  1F7V6PADRZ ', VoucherCodeKind::Purchase];
+        yield 'hyphen without the promo prefix' => ['X-1F7V6PADRZ', VoucherCodeKind::Malformed];
+        yield 'characters outside the code alphabet' => ['1F7V 6PADRZ', VoucherCodeKind::Malformed];
+        yield 'empty' => ['  ', VoucherCodeKind::Malformed];
+        yield 'too long' => [str_repeat('A', 51), VoucherCodeKind::Malformed];
+    }
+
+    #[DataProvider('codes')]
+    public function testClassify(string $code, VoucherCodeKind $expected): void
+    {
+        self::assertSame($expected, $this->classifier->classify($code, new \DateTimeImmutable('2026-10-06')));
+    }
+
+    public function testLegacyCodeIsRecognisedOnItsLastDay(): void
+    {
+        self::assertSame(VoucherCodeKind::Promo, $this->classifier->classify('LW0705', new \DateTimeImmutable('2027-04-30')));
+    }
+
+    public function testLegacyCodeIsAPurchaseCodeOnceExpired(): void
+    {
+        self::assertSame(VoucherCodeKind::Purchase, $this->classifier->classify('LW0705', new \DateTimeImmutable('2027-05-01')));
+    }
+
+    public function testNormalizeTrimsAndUppercases(): void
+    {
+        self::assertSame('R-SOMMER26', $this->classifier->normalize(' r-Sommer26 '));
+    }
+}