Hi, thank you for your wonderful work on oauth2-server package.

According to OAuth 2.0 spec for errors during authorization request, authorization server should return error 'unsupported_response_type' if the response_type parameter is invalid (missing, unsupported value...). The current implementation returns error code 'unsupported_grant_type', which is not in accordance to the spec.

The only place in spec where I see error code 'unsupported_grant_type' is in section 5. Issuing an Access Token.

So, as I understand it, the error code 'unsupported_response_type' should be related to the 'response_type' parameter which is used in authorization request. The error code 'unsupported_grant_type' should be related to the 'grant_type' type parameter which is used in token request.

Best regards