Display names for the external ids the matcher references; see matcherReferencesSql. Empty when it references none.
Composed route display name: ${product.name} · ${product_vendor.name}
for the rule's route. Both columns are NOT NULL and the route join is
INNER, so this is always present.
Admin-tier view of a fee rule = identity columns + the columns of the rule's current version.
idis the identity row's external id; matcher and value columns come from the version pointed to bycurrentVersionId.