Train Travel API: A Modern OpenAPI PetStore Replacement

The Train Travel API is an updated sample OpenAPI description for an imaginary train travel service, replacing the outdated PetStore example. It includes various open data sources and public APIs that demonstrate concepts and patterns used in designing this API. The schema components cover Stations, Trips, Bookings, and Booking Payments, with appropriate web standards usage and adherence to OpenAPI v3.1 conventions. The API design is built for modern JSON Schema and includes examples of polymorphism and variable payloads. Currently, there is no API implementation, but the project encourages feedback and collaboration in evolving and improving the OpenAPI description.