[MM-19914] Fix data races in WebSocketEvent (#13039)

* Make WebSocketEvent type immutable

* Update code to use updated immutable WebSocketEvent type

* Export WebSocketEvent fields and mark them as deprecated

api4/channel_test.go

@@ -1367,7 +1367,7 @@ func TestConvertChannelToPrivate(t *testing.T) {
 		for {
 			select {
 			case resp := <-WebSocketClient.EventChannel:
-				if resp.Event == model.WEBSOCKET_EVENT_CHANNEL_CONVERTED && resp.Data["channel_id"].(string) == publicChannel2.Id {
+				if resp.EventType() == model.WEBSOCKET_EVENT_CHANNEL_CONVERTED && resp.GetData()["channel_id"].(string) == publicChannel2.Id {
 					eventHit = true
 				}
 			case <-stop:
@@ -2426,7 +2426,7 @@ func TestRemoveChannelMember(t *testing.T) {
 		})
 
 		wsr := <-wsClient.EventChannel
-		require.Equal(t, model.WEBSOCKET_EVENT_HELLO, wsr.Event)
+		require.Equal(t, model.WEBSOCKET_EVENT_HELLO, wsr.EventType())
 
 		// requirePost listens for websocket events and tries to find the post matching
 		// the expected post's channel and message.
@@ -2435,7 +2435,7 @@ func TestRemoveChannelMember(t *testing.T) {
 			for {
 				select {
 				case event := <-wsClient.EventChannel:
-					postData, ok := event.Data["post"]
+					postData, ok := event.GetData()["post"]
 					if !ok {
 						continue
 					}