A password change ends every session, but a sign-in or sign-in link checked
against the old password just before the change could still save its session
just after, and that session outlived the change.
The session now checks, as it's saved, that the user's password is still the
one the request loaded. The save's transaction holds SQLite's write lock from
the start, so a change commits either before the check, which fails it, or
after the insert, and ends this session with the others. Sessions start
through the user's association so the check sees the user that was
authenticated, and a refused sign-in is answered like a wrong password.
(cherry picked from commit 19319a1cff)
A transfer link signed only the user id, so one copied before the
password changed still started a session for up to four hours after.
Bind it to the password salt with generates_token_for, so a new
password ends those links too. Links made before this upgrade stop
working; they last four hours at most.
From #371.
(cherry picked from commit 160ba295b5)