Or use an API layer such as GraphQL that doesn’t require versioning for such a minor change since additive changes (or deprecations) to the API do not affect existing queries - each query states exactly what it needs.
But that already qualifies as the boilerplate code that was supposedly the root problem, isn't it?
But now instead of a simple mapper you've bolted on another complex system.
So exactly how does JSON in the db solve any of the problems that were presented? Other than adding two buzzwords, what were the improvements?