Allow site filter query parameters (#99)

Author: stephen-soltesz

handler/handler.go

@@ -192,9 +192,11 @@ func (c *Client) Nearest(rw http.ResponseWriter, req *http.Request) {
 	}
 
 	// Find the nearest targets using the client parameters.
-	t := req.URL.Query().Get("machine-type")
+	q := req.URL.Query()
+	t := q.Get("machine-type")
 	country := req.Header.Get("X-AppEngine-Country")
-	opts := &heartbeat.NearestOptions{Type: t, Country: country}
+	sites := q["site"]
+	opts := &heartbeat.NearestOptions{Type: t, Country: country, Sites: sites}
 	targets, urls, err := c.LocatorV2.Nearest(service, lat, lon, opts)
 	if err != nil {
 		result.Error = v2.NewError("nearest", "Failed to lookup nearest machines", http.StatusInternalServerError)