You can build custom apps for Upsales. Version is one example.
Keep track of which version of your app your users are running. The version the user has configured your app for will be sent as version in the body of the request. Requests sent while the user configures your app (test, fieldValues and config button requests) have no version.
If your app has user-level configuration, the version each user has configured is sent as userVersion. It can differ from version.
So, if your current version is "2.0.0" and a user is still configured for "1.0.0", you could use this information to run older code or notify the user to update. To update, the user saves your app's settings in Upsales. The configured version is then set to your app's current version.