Flesh out web UI for mail a bit to prepare for Herald outbound rules
- Currently, we don't store the headers we actually sent, or the reasons we actually did or did not deliver a mail.
- Start storing these (as headers.sent and actors.sent).
- Show them in the web UI.
- Show them in bin/mail show-outbound (previously, we sort of re-computed them in a hacky way).
- Take them into account in bin/mail volume.
Then some minor changes:
- Show mail bodies.
- Show more mail information.
- Start renaming "MetaMTA" to "Mail", at least in the web UI.
Reviewed By: chad
Differential Revision: https://secure.phabricator.com/D13878