Prevent multiple Service Desk issues created by cc'd recipients using 'Reply All'

Currently when a cc'd recipient (or, I suppose, anyone who has received the email - bcc, fwd, etc) uses Reply-All, another Service Desk issue is created with the contents of their reply.

We should ensure that external participants do not inadvertently create noisy issues this way, as without this check it would create multiple Service Desk issues with all the recipients as external participants.

To reproduce:

1. Send email to a service desk and another email account
2. Service Desk issue gets created -> awesome
3. Reply from the other email account
4. Another Service Desk issue gets created -> ideally this would get added as a note on the original issue iso a new issue

To address:

We should ensure that any reply to an existing SD issue gets added as a note to that issue and not as a new issue. If we can't identify/deduce by subject/content we may need to add metadata somehow?

• we should store message_id from the email and check if the email is not a reply to the email that created the issue