R1:95eeffff7e5d

Terminate other sessions on credential changes

Summary:
Fixes T5509. Currently, existing sessions live on even if you change your password.

Over the course of the program, we've recieved a lot of HackerOne reports that sessions do not terminate when users change their passwords. I hold that this isn't a security vulnerability: users can explicitly manage sessions, and this is more general and more powerful than tying session termination to password resets. In particular, many installs do not use a…