Describe the problem

Now that Flex is adopted, we want to be able to track usage of Flex features within the validator and within the Mobility Database API, which includes features generated by the GTFS Schedule Validator.

Proposed solution

The following four features should be added:

Booking Rules: At least one record in booking_rules.txt
Fixed-Stops Demand Responsive Transit: At least one record in location_groups.txt
Zone-based Demand Responsive Transit: At least a trip in stop_times references only location_id
Deviated Fixed Route: At least a trip in stop_times references location_id AND stop_id AND arrival_time AND departure_time

Alternatives you've considered

No response

Additional context

No response