[fapi] scope & response_type are optional in OAuth parameters

[leleueri]

According to OIDC core when request object is used by value or by reference, the OAuth parameters response_type & scope are required.

BUT the FAPI conformance test suite execute some tests where the response_type and scope parameters are present into the request object passed by reference but missing from the query parameters... these tests shall pass even if the OIDC core specification consider it as invalid...

The reason of this inconsistency comes from the OAuth JAR (currently in draft n°34) that requires only the client_id and the request or request_uri parameters because the other ones MUST be present into the request object...