Solve validation with Joi

So the more of those validate functions i'm writing the more i'm asking myself if this approach is optimal. We are in fact doing 95% schema validation, a task which a library like joi (or maybe the one you wrote, Kent, api-check ?) solves perfectly, but we are writing this very imperatively and with ad hoc, non-normalized error messages.

In fact i am thinking of experimentally starting an alternative approach in another repo, maybe just called webpack-joi-schema and see how far this would replicate the use case of our approach here. The main goal would be finding out where the limits of using a schema validation library would be and maybe check out if the burden of all those manual tests could be "extracted" onto the shoulders of a mature, more generic library -- thereby substantially reducing the error surface.

Review the current validate functions and their manual tests, then compare the existing approach with Joi and api-check as proposed. The issue suggests experimenting in a separate webpack-joi-schema repository; done would require determining how much of the current use case it can replicate and where schema validation falls short.