access deny should not always redirect

[tnclong]

Hi @bodhi @jinzhu

Can you share your thought here?

https://github.com/qor/auth/blob/master/authority/authority.go#L33

https://github.com/qor/auth/blob/master/authority/authority.go#L81

After valid the roles, I want write proto(json) message to front-end instead of redirect to login page.
I think the how to handle access deny is a configurable behavior.

// Config authority config
type Config struct {
	Auth                          AuthInterface
	Role                          *roles.Role
	// RedirectPathAfterAccessDenied string
        AccessDenyHandler func(w http.ResponseWriter, req *http.Request, auth AuthInterface)
}

[tnclong]

Thanks!

47e5e51