Allow to overwrite link to publisher version

In the past, we had cases without DOI (#3 (closed)) and the urlpub field was added. Now there is a case where we do have a DOI, but resolving the DOI does not lead directly to the publisher but to some intermediate useless page that just displays a "you need to allow popups" message. There is a link from there to the real publisher page, but it is really well hidden, so the DOI link is not useful. Of course, I do not want to remove the DOI from the listing.

So please provide a way to replace the link for "Publisher version" with something else even if there is a DOI specified. I guess we can just use urlpub.