Modify codebase to support service worker API changes

[taoeffect]

Problem

#1981 might not be done in time for the release of 1.0, and we want to avoid having to recreate groups when that's finished.

Solution

Create a PR that makes the minimum necessary API changes to Chelonia to avoid recreating groups without actually implementing the service worker PR. (Later on, finish moving Chelonia into the service worker).