Based on your requirements, I can assure you that I have the necessary knowledge and expertise to complete this task efficiently. I have previously developed a Flutter app that successfully decodes GTFS data using Protocol Buffers.
To proceed with the project, I will:
1. Utilize the provided URL and API key to fetch the GTFS data in Protocol Buffers format.
2. Decode the Protocol Buffers data into a `FeedMessage` object using the Dart Protobuf library, as demonstrated in the documentation you shared.
3. Extract the required information from the decoded `FeedMessage` and present it in a suitable format within the Flutter app.
4. Incorporate the additional functionality for handling the extra portion of the protocol, utilizing the provided extra proto files.
I am confident that I can complete this task within 2-3 hours, as I have prior experience working with GTFS data and Protocol Buffers in Flutter. I will ensure that the decoding process is accurate and efficient.
If you are ready to proceed, I kindly request you to provide me with the necessary details, including the URL and API key, so that I can begin working on the implementation.
Best Regards,
Sajjad