Convert PonderAnswer to modular transactions
Summary: Fixes T12624. Converts PonderAnswer over to modular transactions.
Test Plan:
- Add an answer
- Edit an answer
- Hide an answer
- Comment on an answer
Reviewers: epriestley
Reviewed By: epriestley
Subscribers: Korvin
Maniphest Tasks: T12624
Differential Revision: https://secure.phabricator.com/D17811