Add support for SameSite option

[lakhansamani]

How it affects

With the new chrome versions, it will be only supporting Strict mode for cookies, i.e. SameSite=Lax we need to manually set SameSite=None if we want our APIs to work with different domains.

Ref: https://www.chromestatus.com/feature/5633521622188032

Currently, the library is not supporting SameSite option. This is part of net/http package and should be supported

Example

cookie := http.Cookie{
	Name:     "my-cookie",
	Value:     "token"
	Domain:   domain,
	Path:     "/",
	MaxAge:   30 * 60 * 60 * 24,
	Expires:  time.Now().Add(30 * 24 * time.Hour),
	Secure:   false,
	SameSite: http.SameSiteNoneMode,
}

Also, something to note http.SameSiteNoneMode constant is introduced with Golang v1.13.0 only.

Expected outcome:

There should be a way to configure SameSite option