add WSGIPassAuthorization directive to Apache configuration

[guillomovitch]

I spend a few hours debugging this token endpoint authentification issue, which is espcially painful as only basic authentifcation is supported.

For the record, here are the following symptoms:

[satosa.frontends.openid_connect.token_endpoint] invalid client authentication at token endpoint
...
pyop.exceptions.InvalidClientAuthentication: client_id 'None' unknown