feat: answer received form submissions by mail

tests/Config/SeasonCalendarTest.php

@@ -70,4 +70,35 @@ class SeasonCalendarTest extends TestCase
 
         (new SeasonCalendar('xx-yy', '04-01'))->seasonYearFor(new \DateTimeImmutable('2025-01-01'));
     }
+
+    /**
+     * @dataProvider provideUpcomingSeasonDates
+     */
+    public function testTheCurrentOrUpcomingSeasonYear(string $date, int $expected): void
+    {
+        $calendar = new SeasonCalendar('11-01', '04-01');
+
+        $this->assertSame($expected, $calendar->currentOrUpcomingSeasonYear(new \DateTimeImmutable($date)));
+    }
+
+    public static function provideUpcomingSeasonDates(): iterable
+    {
+        // Between two seasons: the winter ahead, which is what a recruiting mail means.
+        yield 'September, before the season starts' => ['2026-09-24', 2026];
+        yield 'the day the season starts' => ['2026-11-01', 2026];
+        // Inside a season: that season, not the next one.
+        yield 'December, mid season' => ['2026-12-15', 2026];
+        yield 'the last day of the season' => ['2027-04-01', 2026];
+        // After a season ended, so the next one to start.
+        yield 'May, after the season ended' => ['2027-05-02', 2027];
+    }
+
+    public function testTheShortLabelIsTheTwoDigitSpan(): void
+    {
+        $calendar = new SeasonCalendar('11-01', '04-01');
+
+        $this->assertSame('26/27', $calendar->shortLabel(2026));
+        // The turn of the century has to stay two digits on both ends.
+        $this->assertSame('99/00', $calendar->shortLabel(1999));
+    }
 }