chore: code cleanup

src/Config/BookingHorizon.php

@@ -0,0 +1,31 @@
+<?php
+
+declare(strict_types=1);
+
+namespace App\Config;
+
+/**
+ * How far ahead a booking may be made.
+ *
+ * Measured from **today**, not from the day being booked: a cap relative to the chosen start date
+ * can be pushed out simply by starting later, which is exactly what the previous
+ * BookingSeries::MAX_MONTHS rule allowed (a series starting in six months could run to month
+ * nine). It governs single bookings and series alike, which is why it lives here rather than on
+ * BookingSeries.
+ *
+ * ROLE_ADMIN is exempt -- see BookingRequest::$unlimitedHorizon.
+ */
+final class BookingHorizon
+{
+    public const MONTHS = 3;
+
+    /**
+     * The last day that may still be booked. Inclusive.
+     */
+    public static function latest(?\DateTimeImmutable $today = null): \DateTimeImmutable
+    {
+        return ($today ?? new \DateTimeImmutable('today'))
+            ->setTime(0, 0)
+            ->modify(\sprintf('+%d months', self::MONTHS));
+    }
+}