Allow middleware to modify request object.

[rohit267]

Goals

1. Should be able to add at least locals object inside request object from middleware.
2. Should be able to access the locals object fromNextPageContext and NextApiRequest

Non-Goals

No response

Background

While using the middleware and not using next-auth, there is not way to add user set in request in middleware.js like we do in express like req.locals.user.

Proposal

I can contribute if someone can explain the directory structure.