Add support for timezones

[Alessandro100]

Currently service date range is saved without timezone support. Introduce timezone support

Tasks

1. Modify the schema in gtfsdataset to make the service date range values support timezone. Default to date time UTC hour 0.
2. In the backfill python function modify the logic to include timezones in UTC. On service_date_range_start, the hour should be midnight and for service_date_range_end the hour should be 11:59pm. If no timezone exists assume UTC hour 0.
3. Assure the feed status update function is being compared in UTC
   -- post answered questions --
4. Modify the schema to include timezone in gtfsdataset
5. Add timezone to the dataset endpoint (will be included in latest_dataset)
6. Display the new service date range and display timezone in UI

Questions

• Do we want to save the timezone in the Feed? or in the dataset [Dataset]
• Do we want to expose the timezone in the API? (Feed endpoint) [yes]
  - Should we display the timezone in the UI? [yes]
• In the UI should the dates be displayed in regards to the user's local timezone or the feed's timezone? [feed timezone]

[emmambd]

My answers to questions that others can push back on it:

1. Since service window is define din the dataset, I'd save timezone on the dataset level
2. Yes to API and UI
3. Feed's timezone