When ECP profile (saml-ecp-v2.0-cs01) is used with PAOS binding Lasso
populates an AuthnRequest with the "Destination" attribute set to
AssertionConsumerURL of an SP - this leads to IdP-side errors because
the destination attribute in the request does not match the IdP URL.
The "Destination" attribute is mandatory only for HTTP Redirect and HTTP
Post bindings when AuthRequests are signed per saml-bindings-2.0-os
(sections 3.4.5.2 and 3.5.5.2). Specifically for PAOS it makes sense to
avoid setting that optional attribute because an ECP decides which IdP
to use, not the SP.