[Zope-CMF] Trying to customize CMF login to use email rather than userid

[Deb Lewis]

Have hunted through all the documentation I can find, bumbled around in base
system code, and searched web sites/news groups, still stumped and figure
this must be something others have done, so must be time for plaintive cry
for help.

Objective: trying to customize the standard login_form for a CMF site to let
members log in by entering the email address from their member data rather
than the userid of their account.

Did a revised login_form, have supporting services to map email value from
form input to a userid and detect cases where that's not possible and actual
userid needs to be supplied, but can't figure out where/how to get this
hooked in properly in the ZPublisher/auth/login mechanism so that the form
submit for this page can get the login processed.

Configuration: Zope 2.7.7, CMF 1.4.8; also GRUF (GroupUserFolder) 3.3

Any pointers to tips/solutions would be greatly appreciated.

Deb Lewis