IDataSource.findById(id: EntityKey): Promise<Record<string, unknown> | null>
Find a single entity by its primary key value.
The key is an EntityKey: a scalar string/number or a
composite record. A composite record is refused by the backend when it
maps to a single column (e.g. Prisma's where: { id }), so widening this
parameter is source-compatible for callers but breaking for an
out-of-repo implementor whose method still declares the scalar-only form.
id: EntityKey
The primary key value (scalar or composite record)