chore: further cleanup and refactor

src/BusProNet/Model/Booking.php

@@ -15,6 +15,8 @@ use App\BusProNet\Constants;
  */
 class Booking
 {
+    public const string STATUS_CANCELED = 'S';
+
     public ?int $id = null;
     public ?int $agencyId = null;
     public ?int $bookingNumber = null;

src/BusProNet/Model/BookingResponse.php

@@ -15,6 +15,10 @@ namespace App\BusProNet\Model;
  */
 class BookingResponse
 {
+    public const string BOOKING_POSSIBLE = 'möglich';
+    public const string BOOKING_IMPOSSIBLE = 'nicht möglich';
+    public const string BOOKING_PROCESSED = 'erfolgt';
+
     /**
      * @param string                $status        Booking status (möglich|erfolgt)
      * @param int|null              $bookingNumber Booking number (BPN XML: vorgang)
@@ -37,7 +41,7 @@ class BookingResponse
      */
     public function isInquiryValid(): bool
     {
-        return 'möglich' === $this->status;
+        return self::BOOKING_POSSIBLE === $this->status;
     }
 
     /**
@@ -45,7 +49,7 @@ class BookingResponse
      */
     public function isBookingSuccessful(): bool
     {
-        return 'erfolgt' === $this->status;
+        return self::BOOKING_PROCESSED === $this->status;
     }
 
     /**