[lib] Reducer for commServicesAccessToken
Summary:
Modelled this on lib/reducers/data-loaded-reducer.js.
Depends on D7241. Linear task: ENG-3389.
Test Plan: Flow
Reviewers: kamil, varun, jon, atul
Reviewed By: atul
Subscribers: tomek
Differential Revision: https://phab.comm.dev/D7269