Summary: We need to go slightly farther to stub reply handler functionality for Ponder in at least some configurations, where we rely on the presence of a unique random key to generate per-object or per-object+user reply addresses. This should probably be formalized in an interface since it's currently pretty ad-hoc. Test Plan: - Made comments in Ponder under a per-user email configuration. - Ran migration, verified mail keys were generated. - Ran migration again (with --apply), verified existing questions were skipped. - Created a new question, verified mail key generation. Reviewers: pieter Reviewed By: pieter CC: aran Maniphest Tasks: T1873 Differential Revision: https://secure.phabricator.com/D3665