Add a way to see emails recently sent by Arooo

[anaulin]

It would be good, for debugging and verification purposes, to have a way for operators to see which emails were recently sent by Arooo (recipient email, content, etc).

Currently we use Amazon SES to send out the emails, but it appears that we do not have the configuration described in Amazon's documentation to store and see sent emails (https://aws.amazon.com/premiumsupport/knowledge-center/ses-email-sending-history/).

Some options to accomplish this would be:

1. Add the Amazon SES configuration linked above. Requires access to DU's AWS console, and some comfort with AWS configuration.
2. Create a new email address (or mailing list), like, say, sent-emails@doubleunion.org, and automatically bcc all Arooo's emails there, using a Rails email interceptor (https://guides.rubyonrails.org/action_mailer_basics.html#intercepting-emails). Requires the ability to create this new email address, and a bit of Rails knowledge.
   2a. A variant on this would be to just bcc all emails to the membership coordinator email (or some other existing email), and let the person that handles that email create a filter to sort out the bcc-ed emails into a label or similar
3. Implement a Rails email observer to create some sort of record of each email sent (https://guides.rubyonrails.org/action_mailer_basics.html#observing-emails). We could let operators just look in the database to see those records, or make a little UI to see them. Requires some Rails knowledge.

I think the second option above is the easiest from a development standpoint, and also the easiest for the Membership Coordinator to use (they would just log into an email account to check what was sent).

/cc @sarahwalters @brittag