Do we need a PolygonArray or PolygonCollection domain type?

[jonblower]

I think we have agreed (#202) that the interpretation of MultiPolygon should be as a single domain element, with a single associated range value that applies collectively to all the constituent Polygons. (This is currently inconsistent with the Playground, which would need to be fixed.) But this leaves an obvious question - how should we encode a situation where we want to associate different range values with each individual polygon? For example, recording the population of each of the countries of Europe.

Maybe we need a new domain type - perhaps PolygonArray or PolygonCollection? The domain would look structurally similar to a MultiPolygon but the associated range would be different.

This would also imply a need for a PolygonCollectionSeries.

[jonblower]

It might also imply the need for a MultiPolygonCollection!! This would be needed for the use case of "give me the population of each of the European countries, associated with the geometries of all their individual constituent territories".

In reality, I wonder if this would be just too confusing, and maybe the Coverage would just associate country codes with population values. There might be a separate lookup to associate country codes with geometries (GeoJSON features).