Build a reservation system for a predefined set of conference rooms given as a list of room IDs [roomA, roomB, ...].
It should have a method like scheduleMeeting(startTime, endTime) that should return a reservation identifier (including roomId) and reserve it, or return an error if no rooms are available.
This problem asks you to design a meeting room reservation system for a fixed set of room IDs. The main operation, scheduleMeeting(startTime, endTime), should find an available room whose existing bookings do not overlap with the requested interval, reserve it, and return a reservation identifier that includes the roomId. If every room is busy for that time range, the method should return an error or failure. A typical solution uses per-room schedules with interval conflict checks, plus a strategy for efficiently selecting an available room.
