See
- Add dynamic scripting-language transformation service by jimtng · Pull Request #3487 · openhab/openhab-core · GitHub for the change.
- Transformations | openHAB for the updated docs
- openHAB 4.0 SNAPSHOT discussion - #320 by rlkoshak for the docs presented in a different way, mostly focused on from the UI perspective.
The tl;dr is the rules language being used drives the service ID instead of the generic SCRIPT for all languages. You can now also use an appropriate file extension based on the language used (e.g. use mytransform.js instead of mytransform.script). Finally, there is now support for creating transformations through the UI.