Include a warning/update in the HTML report that Flex rules have not been added to the validator yet

[emmambd]

Describe the problem

Some stakeholders have expressed confusion that they're getting invalid errors, because Flex rules have not been implemented in the validator yet. We should include a notice in the html reports that Flex rules are yet to be implemented.

Proposed solution

Display an alert in HTML validation report when any Flex feature is registered:

• Booking Rules
• Predefined Routes with Deviation
• Zone-based Demand Responsive Services
• Fixed-Stops Demand Responsive Services

e.g "Not all GTFS-Flex validation rules have been added yet. This work is still in progress. You can manually review all the validation rules for Flex data here."

Should display at the top of the page. Can use a similar style to the alerts on the Mobility Database, but in black and white: https://mobilitydatabase.org/feeds/mdb-934

Alternatives you've considered

No response

Additional context

No response

[cka-y]

Needs #1844 to be merged since there were some changes in the features naming for flex features.

[qcdyx]

Clarification: @emmambd Shall we also add the alert on the Web UI?

Tasks:

• add the logic based on the proposed solution
• display the alert on the HTML report and the Web UI
• add tests

[cka-y]

@emmambd could you please validate that the requirements are:

• Add an indicator in the html report when flex features are detected
• Add a generic indicator in the web UI

[emmambd]

Just in the HTML report, please!