Upgrade Sendgrid to the modern mailer API; removes "api-user" option
Summary:
Ref T920. Ref T5969.
- Update to the new "$message" API.
- Update to Sendgrid v3.
- Add a timeout.
- This removes the "api-user" option, which Sendgrid no longer seems to use.
Test Plan: Sent Sendgrid messages with bin/mail send-test ... using subject/headers/attachments/html/to/cc.
Reviewers: amckinley
Reviewed By: amckinley
Subscribers: jbrownEP
Maniphest Tasks: T5969, T920
Differential Revision: https://secure.phabricator.com/D19960