handle_logout_request doesn't sign redirect binding responses as requested

[MrkGrgsn]

When saml2.client:handle_logout_request() is called with sign=True and the selected binding is HTTP Redirect, the request is not signed.

Where the error lies is not clear. apply_binding() accepts a sign param but it is not used for redirect bindings. It instead looks for the sigalg param in kwargs. handle_logout_request() supplies neither the sign nor sigalg params to apply_binding()

[peppelinux]

#595

At this time I found In examples/ idp that it doesn't handle signed logout request

[peppelinux]

I done a SLO implementation here:
https://github.com/peppelinux/djangosaml2idp/blob/master/djangosaml2idp/views.py#L317

It works even if SLO request is signed

[peppelinux]

Moving all the aspect of signature in HTTP-REDIRECT binding here:
#633