This diff checks if the fid stored in the synced metadata table store is still valid. We could run into this situation, if a user connects their facaster account to their comm account, then later deletes their farcaster account, but their comm account still has the old deleted fid. If this is the case we should unlink this fid from the user's comm account
Linear task: https://linear.app/comm/issue/ENG-7277/check-if-the-user-fid-stored-in-the-synced-metadata-table-is-still
Depends on D12569