Please highlight that attributes.create(attr_spec) only applies to source: Doc improvement

[nw298]

💁 Possible Solution

It'd be helpful if there was a note that explains that attributes.create(attr_spec) should be applied to only source datasets and not unified datasets.

[skalish]

I believe the issue here is that creating attributes that appear in the unified dataset must be done using the projects/{project_id}/attributes endpoints. This should be captured in a tutorial explaining how to create unified attributes.

This should be reflected in the modeling of such attributes in tamr_client, probably as a new dataclass UnifiedAttribute that is handles creation (and other) actions appropriately. We could potentially put in some safeguards to prevent attempts to create attributes on UnifiedDataset objects too.