• Split user and author functionality into different bots. With this change, the authors and users app packages now have different bot IDs, which enables you to use app permission policies to control access to the authors app. (In previous versions, using app permission policies with Company Communicator led to intermittent message delivery failures.)
• Include a Powershell script for deployment and upgrade from v3. The script checks for deployment prerequisites, creates and configures AAD applications, and deploys the resources to your Azure subscription. It can also detect and recover from some Azure deployment failures.
• Set isNotificationOnly to true in the app manifest. This was originally set to false to allow for recovery in case we missed the conversationUpdate activity, but now that we can get the chat thread ID via Graph, we can set this to true.
• Add unit tests for message send and preparation functions

Please see the wiki for upgrade instructions from Company Communicator v3.