Add a way to query raw data directly from coordo

We need to be able able to query specific data from a datapackage, especially for the dashboard.

I think that defining a "sources" dictionary in the config, with params moved from to the "datapackage" layer, and then adding a route in handle_request which serve that source data would do the job.

Then we should reference that source from the datapackage layer, and move the code around so it all works as before.

That way frontend can freely request "raw" data directly from a source, and maplibre can also use that same endpoint.

This will also prepare the code so we will be able to have different kind of "renderers" (we can think of the map module as a "map renderer" but in the future we could need a "graph" renderer, etc.)

Start by tracing the config, datapackage layer, and handle_request entry point mentioned in the issue. Define how a sources dictionary and source-data route should connect to datapackages, then verify that existing behavior remains unchanged and that raw data can be requested by the dashboard and map renderer.