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/webhook_test.go

@@ -45,9 +45,9 @@ func TestWebhooks(t *testing.T) {
 	require.NoError(t, err)
 	defer finish()
 
-	for _, useSinglePeerConnection := range []bool{false, true} {
-		t.Run(fmt.Sprintf("singlePeerConnection=%+v", useSinglePeerConnection), func(t *testing.T) {
-			c1 := createRTCClient("c1", defaultServerPort, useSinglePeerConnection, nil)
+	for _, testRTCServicePath := range testRTCServicePaths {
+		t.Run(fmt.Sprintf("testRTCServicePath=%s", testRTCServicePath.String()), func(t *testing.T) {
+			c1 := createRTCClient("c1", defaultServerPort, testRTCServicePath, nil)
 			waitUntilConnected(t, c1)
 			testutils.WithTimeout(t, func() string {
 				if ts.GetEvent(webhook.EventRoomStarted) == nil {
@@ -70,7 +70,7 @@ func TestWebhooks(t *testing.T) {
 			ts.ClearEvents()
 
 			// another participant joins
-			c2 := createRTCClient("c2", defaultServerPort, useSinglePeerConnection, nil)
+			c2 := createRTCClient("c2", defaultServerPort, testRTCServicePath, nil)
 			waitUntilConnected(t, c2)
 			defer c2.Stop()
 			testutils.WithTimeout(t, func() string {