Terrasoft.utils is a legacy/classic js module - not created for Freedom UI - although most of it will all still work with Freedom UI code. @creatio-devkit/common is the newer js classes created to work specifically with Freedom UI.

The docs for the legacy js can be found here: https://academy.creatio.com/api/jscoreapi/7.15.0/index.html

There is not yet an equivalent for Freedom UI js classes in @creatio-devkit/common - you can see what exists (without any definition or explanation) here https://www.npmjs.com/package/@creatio-devkit/common?activeTab=code

Ryan