FIX: Capture CC addresses for forwarded emails (PR #14254)

When forwarding emails into the group inbox, we now use the original sender email as the from_address since 2ac9fd9. However, we have not been saving the original CC addresses of the forwarded email, which are needed to include those recipients in on the conversation when replying via the group inbox.

This commit captures the CC addresses on the incoming email, and makes sure the emails are created as staged users and added to the list of topic allowed users so they are included on CC’s sent by the GroupSmtpEmail and other jobs.

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