Service for price categories

[developeregrem]

To calculate an invoice in advance and to automatically create invoice items, we must write a service for price classes.

• Input: Reservation object, type (room price|other)
• Output: List of price categories sorted by date and the date for which it applies.

conditions:

• Display active categories only
• Price categories with a time period have a higher value than categories that always apply.
• Respect origin (ReservationOrigin)

Assumes ticket #9 is done.