Enhancement Request: Tracking traffic from Unpaywall

[cajunjoel]

The question arose among us that there was no mechanism to know when the Unpaywall extension is used to direct traffic to our site (we are a publisher). Since the Green Tab only offers a URL, my suggestion is to append a query string to the destination URL in the Green Tab.

Example:

https://www.publishersite.com/article/Complicated-Research.pdf?unpaywall=1

or if there is an existing query string, the code would need to determine this and react accordingly:

https://www.publishersite.com/article/Jurassic-Park-Journal.aspx?vol=12&issue=3&article_id=23677&unpaywall=1

This does not allow the destination site to (easily) track incoming unpaywall references via something like Google Analytics, but it's a good step towards knowing our impact.

If this is something Unpaywall is interested in including, I'll fork, code, and make a pull request.