Add new page-id field to JavaScript tracker and Serde

[alexanderdean]

Currently SnowPlow tracks the page name and page URL - but these are not very precise from an analytics perspective:

1. What if a new version of the page is launched on the same URL?
2. What if split testing means two different users see different versions of the page on the same URL?

The idea then is to allow the JavaScript to set a custom page-id:

setPageId('<<CMS/JavaScript generated page ID>>');

Then obviously this page ID would need to be passed through on the querystring and then extracted by the Serde...

The alternative to this approach would be to have a big, constantly changing lookup table on the analytics side when different versions of pages went live - and even this wouldn't meet the A/B testing requirement.

[alexanderdean]

Assigning to Yali to get his thoughts...

[alexanderdean]

Closing this as we have a much cooler and more general solution in mind...