[MM-10519] Send websocket event whenever the channel has changed it's type (public|private) (#8798)

* send websocket event whenever the channel has changed it's type (public|private)

* updated per comment

Signed-off-by: Saturnino Abril <saturnino.abril@gmail.com>

* add channel_converted websocket event

Signed-off-by: Saturnino Abril <saturnino.abril@gmail.com>

* only send channel_id via websocket message for "channel_converted" event

Signed-off-by: Saturnino Abril <saturnino.abril@gmail.com>

model/websocket_message.go

@@ -14,8 +14,9 @@ const (
 	WEBSOCKET_EVENT_POSTED                  = "posted"
 	WEBSOCKET_EVENT_POST_EDITED             = "post_edited"
 	WEBSOCKET_EVENT_POST_DELETED            = "post_deleted"
-	WEBSOCKET_EVENT_CHANNEL_DELETED         = "channel_deleted"
+	WEBSOCKET_EVENT_CHANNEL_CONVERTED       = "channel_converted"
 	WEBSOCKET_EVENT_CHANNEL_CREATED         = "channel_created"
+	WEBSOCKET_EVENT_CHANNEL_DELETED         = "channel_deleted"
 	WEBSOCKET_EVENT_CHANNEL_UPDATED         = "channel_updated"
 	WEBSOCKET_EVENT_CHANNEL_MEMBER_UPDATED  = "channel_member_updated"
 	WEBSOCKET_EVENT_DIRECT_ADDED            = "direct_added"