Examples:
CUSTOMSTAYFEE 2 CITY_TAX GUESTNIGHT AGEFROM=6 AGETO=64 will send 2 citytax for each guest between the age of 6 and 64per night to be collected at the accommodation
CUSTOMSTAYFEE 2 CITY_TAX GUESTNIGHT AGEFROM=6 will send 2 citytax for each guest from the age of 6 to be collected at the accommodation