referrer tracking

This tracks which page an individual user came from to reach the site as well as which page they came from to get to the sign up form. It stores a raw URL, exportable to csv, that we can analyze later.

This is useful because if a user came from the apply page, it means they are probably interested in applying, etc. If they came externally from Google searching for the keywords "job opportunity", we might be able to use that when reaching out to them too.
> Log and save kinda mean the same thing in my mind... but all that function does is save the first referrer it sees (and only the first, this is for the external url that got them into our site, not internal links) to the session cookie so we can refer back to it later.

It's a small nit-pick, but I would rename it save_external_referrer or log_external_referrer .  When I first read "log", I thought, oh it's going to write it somewhere.  Then I looked at the code and saw that it just stored a value in session.  Then I was confused about whether I should be paying attention to this code and had to go look elsewhere to see where the saved value was used.  Then it started to make sense, but I still questioned it because of the name.  If it was just called save_external_referrer it would have been immediately obvious and would have saved time.  This sort of thing happens over and over again over time as people try to read, fix, and change code so that's why I took the time to write out this paragraph :)