Publish database prices

Register your own managed database rates so CostGraph can price clusters it has no public price for. An entry is upserted on its natural key (provider, service, region, engine, edition, instance type and usage type), so re-posting the same entry with a new cost keeps its id and reprices everything already using it. The returned id is what you attach to a database with the costgraph.ai/pricing-id.database label or tag.