Add 'Schedule' entity to dynamically schedule broadcast

[alexpado]

Current Issue: When the episode count of an anime increase, it will not reflect on the schedule. When the episode count of an anime changes, it can remove broadcast if the episode count decreased, but if it increases, it will not schedule the required event when the anime has been initially scheduled using time shift modified (mainly weekly).

Solution: Create a Schedule entity that is associated to an Anime. When a Broadcast ends, the code should lookup for a Schedule associated to the Anime that has been watched. The Schedule entity will then be used to determine if another Broadcast should be scheduled.

Proposed Structure:

id: long
anime: Anime
shift: Duration
lastScheduledTime: ZonedDateTime

Benefits:

1. Even if the Anime episode count change, as Broadcast are scheduled on the fly, it will work just fine.
2. To delay all scheduled event, the Schedule lastScheduledTime can be updated to shift all future Broadcast times. Schedule should not use the Broadcast time directly as it would not allow individual delays.