check_data_quality: reinstate check on item classification schemes

[duncandewhurst]

This isn't covered in Pelican

[jpmckinney]

@yolile Do you have any memory of this check?

[yolile]

Not really, but I suppose it is around checking whether a scheme exists and if it is valid. I'm not sure if this also included checking if the value item/classification/id is indeed part of the declared schema.

[jpmckinney]

Aha, so that would fit under the "Ground truth" heading I added to group some existing checks.

[jpmckinney]

I think this notebook contains the cells to be reinstated (basically, it unions the item classification schemes across tender, award and contract).

I don't think we can realistically "ground truth" classification IDs, as there can be thousands. But, we can at least check the schemes. (We can maybe add a query to produce a small sample of IDs to check.)