Specify the object type in the object metadata

[TomAugspurger]

If I'm reading https://github.com/zarr-developers/geozarr-spec/blob/main/geozarr-spec.md correctly, there are a few types defined by geozarr:

• DataArray
• Coordinate
• Auxiliary Data (should this be "Auxiliary Variable" or just "Auxiliary"? The header says "Data" but the text says "variable")
• Dataset

Could we amend the spec to require a field indicating the class / type an object represents? This will make it easier for tools to validate correctness.

Without this, I think that tools would need to infer based on _ARRAY_DIMENSIONS / dimension_names (zarr v3).

• DataArray: one or more dimensions not equal to the name of the array, maybe?
• Coordinate: exactly one dimension equal to the array name
• Auxiliary Data: exactly zero array dimensions
• Dataset: a Zarr Group

This might be unambiguous but it'd be much simpler to require a type field. Then you can catch issues with dimension_names itself, like a Coordinate field not having dimension name equal to itself.

This is common in other standards like STAC and OGC Features, which includes a required type field indicating whether an object is an Catalog, Collection, Feature, etc.