Validates one serialized supply chain object (SCO) for a website and verifies the sellers it declares against the published authorized-seller records (ads.txt / app-ads.txt) and the sellers.json entry of each declared seller. Send the serialized SCO string as sco and the publisher domain as id. The response reports a status of valid, invalid, or error, together with the reasons codes behind that verdict — covering both problems with the SCO itself (101, 102) and problems with the authorization of the entities it declares (201-209).