I mentioned this in #770, but I think this deserves its own issue. If you call Obtain() and the solver fails, there's no way for a consumer of the lego API to get the authorization URI in order to deactivate it or retry it at a later date.

The URL member of ProblemDetails might have this information, but I'm not seeing it in any of the errors I'm getting back, except those for invalid nonces. Even if it did, it's not clear to me how I would be able to tell the difference between different kinds of failure.