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20130701 (Monday, 01 July 2013)
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Lino has a first code contributor: 
Josef Kejzlar contributed the new 
:attr:`auth_middleware
<lino.ui.Site.auth_middleware>` setting:

  I need to make custom authentication (to LDAP) and therefore I had 
  to allow replacing authentication middleware. I've also moved 
  authenticate method into middleware class, so that it is possible 
  to reimplement auth.authenticate method that login view uses. The 
  change is backward compatible because auth.authenticate method is 
  reimplemented and all tests passes. I think it could be useful for 
  others as well. Especially the reimplementable auth.authenticate 
  method could be handy.


AFAICS we can remove the module-level 
`get_auth_middleware` and `authenticate` 
functions.

EDIT 20130704: both are indeed necessary, 
and they didn't work
when :attr:`auth_middleware
<lino.ui.Site.auth_middleware>`.