RFC 6749#4.1.2.1 - fix order of error handling #565
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According to https://tools.ietf.org/html/rfc6749#section-4.1.2.1, only when the
redirect_uri&client_idwere correct, the authorisation server should inform the client that user had denied access.The change is to move validation of resource owner approval after the
redirect_uri&client_idvalidation so the correct redirect url is computed.