Email paste link
Summary: Fixes T4878
Test Plan:
- Go to paste
- Add comment
- Check that paste subsribers got paste link by email
See T4878 for more details.
Reviewers: epriestley, #blessed_reviewers
Reviewed By: epriestley, #blessed_reviewers
Subscribers: epriestley, Korvin
Maniphest Tasks: T4878
Differential Revision: https://secure.phabricator.com/D8861