Include the oauth setup URL in the error message

When the JIRA issue validation fails because there is no oauth token,
give the user the URL to use to create the trust relationship.

This is a much better user experience than telling the user to go and
find a commit in the web UI with a JIRA issue and click on it.
I was thinking about this, and I'm wondering if maybe this should just not use ApplicationLinkResponseHandler at all? If we just call req.execute() directly, then won't the underlying infrastructure throw the exception for us? I think that the response handler is meant to handle a response, which we can't do from a push request.

I haven't tested that though.....