Add support for WaterSchedules as a separate resource and allow for multiple per Zone

[calvinmclean]

Description

It would be nice to be able to define more complex WaterSchedules for a Zone. This would allow for watering a Zone multiple times in one day (such as morning/evening, mid-afternoon top-off, or a multiple short soaks for even, deep watering). A complex configuration like this might be annoying to work with as a JSON object nested under a Zone. Also, after putting careful consideration into the WaterSchedule, you might want to use it in multiple Zones without reconfiguring.

Requirements

• Manage WaterSchedules as separate API resources, independent of Gardens or Zones
• Reference by ID in a Zone
• WaterSchedules run independent of Zones as their own scheduled "thing" and it will check for any eligible Zones when it executes
  • This results in fewer scheduled Jobs needing to be managed if I have multiple Zones using the same schedule
  • Manual delaying of watering can go back to the old way of keeping a counter on a Zone of the number of skips, or more likely a timestamp saying the next time it can be watered
  • Possible annoying thing or issue with this implementation is that next_watering_time and weather_data is now tied to the WaterSchedule + Zone. I will implement the response on the WaterSchedule API and then the ZoneResponse can use the same methods and compensate for any configured skips