Exception based scheduling

[br648]

Checklist

• Appropriate branch selected (all PRs must first be merged to dev before they can be merged to master)
• Any modified or new methods or classes have helpful JavaDoc and code is thoroughly commented
• The description lists all applicable issues this PR seeks to resolve
• The description lists any configuration setting(s) that differ from the default settings
• All tests and CI builds passing

Description

The crux of this feature is to allow calendar dates (which are not associated to a calendar, as this is already imlemented) to be loaded, snapshotted and exported without the need to be joined to a calendar. This then allows calendar date services to be defined in their own right and not tied to a calendar.

From the spec (https://developers.google.com/transit/gtfs/reference#calendar_datestxt) this will allow the alternative approach to using calendar dates.

It should be possible under the UI to define a calendar date service by providing the following:

• Exception name. This will be used as the service id, so will need to be unique.
• New schedule type of "CALENDAR_DATE_SERVICE" with a value of 10.
• A single date.

It is assumed that:

• Only active service dates are provided (exception_type: 1).
• That the existing process for submitting this data to the backend will not need altering (testing will confirm either way).

[binh-dam-ibigroup]

Need to play with this code more, but see my comments so far.

[binh-dam-ibigroup]

I'm able to replicate a correct export of a schedule exception not linked to a calendar (with some cheating), so I will go ahead and approve subject to the refactorings I mentioned in my previous comment.

[philip-cline]

Code looks good, but right now I'm a bit confused about the use of the ScheduleException name as the service_id for a calendar_date based service. For example, calendar_dates may be used to add service on 2023-05-29 and 2023-07-04 for a service ID "4" which does not exist in calendar.txt. These would be represented as two separate calendar_dates but right now result in two separate ScheduleExceptions but with the same name. How should this use case be handled if we requiring name to be unique?

[br648]

Code looks good, but right now I'm a bit confused about the use of the ScheduleException name as the service_id for a calendar_date based service. For example, calendar_dates may be used to add service on 2023-05-29 and 2023-07-04 for a service ID "4" which does not exist in calendar.txt. These would be represented as two separate calendar_dates but right now result in two separate ScheduleExceptions but with the same name. How should this use case be handled if we requiring name to be unique?

@philip-cline How does this look? If the calendar date is not assoicated with a calendar the name is made up of service id and the first date. For only-in-calendar-dates-txt-20170916 there is only one entry so strictly speaking the appended date is not needed, but for consistency I've kept it.

[philip-cline]

Thanks yeah this is looking good. I'll start on a front end PR for this.

[philip-cline]

LGTM to me now