feat: special treatment of participants with age 0-2 (babies)

src/BusProNet/Constants.php

@@ -64,4 +64,8 @@ final class Constants
     // Payment type IDs for API
     public const PAYMENT_TYPE_ID_TRANSFER = 2;
     public const PAYMENT_TYPE_ID_DEBIT = 5;
+
+    // Baby room constraints
+    public const BABY_MAX_AGE = 2;
+    public const BABY_ROOM_CODE = 'Baby';
 }