Add CORs headers and OPTIONS support

[austinpray]

ty @jhliberty

• CORs
• OPTIONS middleware

[austinpray]

Almost forgot that we should not be using the * options for the Access-Control-Allow-Origin header. http://www.w3.org/TR/cors/#security

return func(w http.ResponseWriter, r *http.Request) {
        if origin := r.Header.Get("Origin"); origin != "" {
            w.Header().Set("Access-Control-Allow-Origin", origin)
        }
}

[austinpray]

To support OPTIONS we could create a simple lambda that returns a preflight response handler

Then do

router.HandleFunc("/current_action", GetCurrentAction).Methods("GET")
router.HandleFunc("/current_action", NewPreFlightHandler("GET")).Methods("OPTIONS")

And then for more complicated endpoints

router.HandleFunc("/complicated", GetComplicated).Methods("GET")
router.HandleFunc("/complicated", CreateComplicated).Methods("POST")
router.HandleFunc("/complicated", NewPreFlightHandler("GET", "POST")).Methods("OPTIONS")

[austinpray]

I think this works but it needs to be added to the other endpoints