Handle assertion of HTTP-redirect for a LogoutResponse in auth-saml2
The logout process was functional but Peertube was showing an 404 error while handling the LogoutResponse. Maybe Peertube v2 was simply redirecting to the root page instead of showing a 404 ?
This adds an endpoint to capture the HTTP-redirect.
This also prevents the assertion of the saml LogoutResponse with
post_assert as it is not an SamlResponse and will throw an error.