Request and Writer Getters in Context

[grachevko]

Description

While implementing middlewares as a separate module it require to add go-gin as direct dependncy.
Having getters will be able to define interface on client side https://100go.co/#interface-on-the-producer-side-6

That allow to provide implementation to client, but without unnecessary dependencies in case of client doesn't need it

How to reproduce

package middleware

import "net/http"


type Context interface {
	GetRequest() *http.Request
}

func (m *Middleware) HTTPMiddleware(c Context) {
	logger.Info("request", log.String("method", c.GetRequest().Method))
	c.Next()
}

#2281