Login and the OIDC fallback match emails case-insensitively, but the
password reset lookup and the admin create and edit checks compared
exactly. An account stored as Foo@x.com never got a reset mail, and an
admin could create bob@x next to Bob@x, after which login picked
whichever row came first. The signup collision check and the first-user
count also move inside the signup transaction.
Maurice
63f7eab4bb