Add method to get most viewed authors from GA

[cdrini]

Want a way to get most viewed authors in the past e.g. week from google analytics.

Describe the problem that you'd like solved

Having a way to query google analytics from openlibrary repo would be super useful in letting us show "trending" data. As a basic first step, let's get trending authors.

Proposal & Constraints

• [ ] Cache aggressively; like maybe daily? Maybe weekly?
• [ ] Will need to GA API keys to production environments

Additional context

• https://developers.google.com/analytics/devguides/reporting/core/v4/quickstart/service-py

Stakeholders

[BrittanyBunk]

I don't truly know, but would assume it's when the user goes to the site: "Determines how many milliseconds elapsed between the user navigating to the page and the current time" (1) using maybe a timestamp.

I think people use jquery, but I'm really not sure - as I haven't done this before or use pre-existing modules. The python is a different process, so whichever works.

I looked on Graphite and it just shows total author views, so it's not there.