MM-10254 Add plugin APIs for getting/updating user statuses (#9101)

* Add plugin APIs for getting/updating user statuses

* Add and update tests

* Updates per feedback

api4/status.go

@@ -78,7 +78,7 @@ func updateUserStatus(c *Context, w http.ResponseWriter, r *http.Request) {
 
 	switch status.Status {
 	case "online":
-		c.App.SetStatusOnline(c.Params.UserId, "", true)
+		c.App.SetStatusOnline(c.Params.UserId, true)
 	case "offline":
 		c.App.SetStatusOffline(c.Params.UserId, true)
 	case "away":