Standard - 4.1. Check ID Request should include the verification pointer

[Nat Sakimura]

Add

{{{ Upon receipt of the Check ID Request, the Check ID Endpoint should verify the request in accordance with the section 5.3. Check ID Request Verification of the <xref target="OpenID.Messages">OpenID Connect Messages 1.0</xref>.

If any error was found, the endpoint MUST return the error response. }}}

[Nat Sakimura]

duplicate.