Make new path for signalling v1.5 support. (#4180)

* Make new path for signalling v1.5 support.

To be able to support newer clients to interact with older servers, move
signalling v1.5 to new path (`/rtc1`). On the new path, `join_request`
is required and single peer connection is used.

With the existing path `/rtc`, single peer connection is still supported
if `join_request` is used.

Newer clients connecting to old server should follow
1. Try new path WebSocket
2. If that fails, try new path validate at `/rtc1/validate`.
3. If the above gets a 404 which will happen with older server, revert
   back to old path and signalling 1.0.

Open to suggestions on path name.

* test on both paths

* change path from /rtc1 -> /rtc/v1

* test all rtc service path combinations

test/client/client.go

@@ -135,17 +135,22 @@ type Options struct {
 	SignalRequestInterceptor  SignalRequestInterceptor
 	SignalResponseInterceptor SignalResponseInterceptor
 	UseJoinRequestQueryParam  bool
+	RTCServicePath            string
 }
 
 func NewWebSocketConn(host, token string, opts *Options) (*websocket.Conn, error) {
-	u, err := url.Parse(host + "/rtc")
+	rtcServicePath := "/rtc"
+	if opts != nil && opts.RTCServicePath != "" {
+		rtcServicePath = opts.RTCServicePath
+	}
+	parsedURL, err := url.Parse(host + rtcServicePath)
 	if err != nil {
 		return nil, err
 	}
 	requestHeader := make(http.Header)
 	SetAuthorizationToken(requestHeader, token)
 
-	connectUrl := u.String()
+	connectUrl := parsedURL.String()
 	if opts != nil && opts.UseJoinRequestQueryParam {
 		clientInfo := &livekit.ClientInfo{
 			Os:       runtime.GOOS,
@@ -205,6 +210,7 @@ func NewWebSocketConn(host, token string, opts *Options) (*websocket.Conn, error
 		connectUrl += encodeQueryParam("sdk", sdk)
 	}
 
+	logger.Infow("connecting to", "url", parsedURL.String())
 	conn, _, err := websocket.DefaultDialer.Dial(connectUrl, requestHeader)
 	return conn, err
 }