Send data-related warnings from backend in HTTP header and view frontend in respective modules

[rubenthoms]

This PR is aiming to implement #822.

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• ASGI Middleware wrapping router functions in context, enabling them to use an add_warning function to collect warnings while data is generated
• Data sent in HTTP header "Webviz-Content-Warnings" (see https://datatracker.ietf.org/doc/html/rfc6648 and https://beeceptor.com/docs/concepts/http-headers/)
• Data received frontend and assigned to respective module

Remaining challenges/questions

• Tanstack Query is caching the responses of the API requests and is, hence, not calling the API function every time - how to cache/invalidate the warnings from backend such that only warnings for the actually visualized data are shown?
  • Add a default select to TanstackQuery and rather send the warnings as data and let users handle them in module? -> more complex module code and refactoring required; problematic when module authors want to make use of their own select functions as they have to implement the logic themselves.
  • Add a custom wrapper around useQuery?