IDP03 unsolicited sso support

[Peter Schober]

* Alexander Galilov <alexander.galilov at gmail.com> [2015-05-07 14:56]:
> 2015-05-07 15:49:33,070 - ERROR
> [org.opensaml.saml.saml2.binding.security.impl.SAML2AuthnRequestsSignedSecurityHandler:75]
> - SPSSODescriptor for entity ID 'https://authtest.my.salesforce.com'
> indicates AuthnRequests must be signed, but inbound message was not signed

If that vendor indeed communicates (via SAML metadata) that the
authentication requests it generates need to by signed by it, then
they better start generating authentication requests.
I'd open a support request for them to get SP-initiated SSO working,
instead of messing around with IDP-initiated.
-peter