Get only the fields we need

Depending on the data, it might be quite wasteful to get all fields using the
DataStore API. We can optimize a lot by simply getting what we need.

We'll need to change Recline's CKAN API to fix this.

Start by reading the Recline CKAN API integration and tracing how DataStore requests are built for map and choropleth views. Identify where the requested fields are determined and confirm the expected behavior for each data shape. Done means the API requests only the fields needed by the view rather than retrieving every field.

Written by the indexing model from the issue text.