Summary: Ref T6960. Ref T13217. Ref T13216. Depends on D19811. Use the recently-introduced "%P" conversion ("Password/Secret") to load sessions in SessionEngine. This secret isn't critical to protect (it's the //hash// of the actual secret and not useful to attackers on its own) but it shows up on every page in DarkConsole and is an obvious case where `%P` is a more appropriate conversion. Test Plan: Note "*********" in the middle of the output here, instead of a session key hash: {F6012805} Reviewers: amckinley Reviewed By: amckinley Maniphest Tasks: T13217, T13216, T6960 Differential Revision: https://secure.phabricator.com/D19812