Ensure all SecWG members have the same/correct permissions on the security@openedx.org mailing list/group

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• Make sure everyone can send on behalf of the security@openedx.org
• Make sure the on/off-boarding docs reflect the the permiissons members should receive.
• Turn on collaborative inbox?
• Add instructions on how to use collaborative inbox on "For working group members" page?

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• What are the best practices for using the collaborative inbox?
• Put in some screenshots for the runbook for responding to e-mails.

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This is all set, all members can manage the mailing list.