feat: expose hotel cost unit and iso country code via the api

src/BusProNet/Model/Hotel.php

@@ -35,4 +35,15 @@ class Hotel
 
     #[Groups(['api:list', 'api:single', 'snapshot'])]
     public ?string $country = null;
+
+    /**
+     * Raw `kostenstelle`, deliberately a string: coverage is thin and some hotels carry a
+     * space-separated list such as "84 85", so it is an opaque label, not a number.
+     */
+    #[Groups(['api:list', 'api:single', 'snapshot'])]
+    public ?string $costUnit = null;
+
+    /** {@see \App\BusProNet\Utility\CountryCodeMapper} — lowercase ISO-2, null when unmappable. */
+    #[Groups(['api:list', 'api:single', 'snapshot'])]
+    public ?string $countryCode = null;
 }