Generate middlewares as fields

[karitham]

This PR cleans up the ugly middleware map in favor of a clean, generated struct.

The goal is to profit from the excellent autocompletion provided by IDEs to work faster.

As an added bonus, if you had previously used a middleware and forgot it in the spec, the code wont compile, as opposed to silently running, ensuring not ever forgetting a middleware both in the code and in the spec (If you've never typed it, I can't do anything for you)

[karitham]

Before:

	mw := map[string]func(http.Handler) http.Handler{
		"pathMiddleware": func(h http.Handler) http.Handler {
			called = true
			return h
		},
		"operationMiddleware": func(h http.Handler) http.Handler { return h },
	}

After:

	mw := Middlewares{
		Path: func(h http.Handler) http.Handler {
			called = true
			return h
		},
		Operation: func(h http.Handler) http.Handler { return h },
	}