Add referrer overwriting

[Khodl]

This change should allow the admin to overwrite the domain. It would also solve #48 by allowing the server to include the referrer provided by Cloudflare server-side.

⚠️ As I am not really familiar with that stack, I did not test it.

[adriaandotcom]

I think that referrer should be changed for any further pages, right?

Otherwise it's always the page before landing.

Hm, it seems to always be the page before landing anyway.

[Khodl]

From my understanding, here is the current scenario with Cloudflare when I arrive at my website (Untalent) from Google:

• Captcha page:

  • SimpleAnalytics script: not loaded?
  • Server referrer: n/a, Cloudflare manages this page
  • Client referrer: n/a, handled by Cloudflare
  • → Redirects to the next page.

• Next page:

  • SimpleAnalytics script: loaded.
  • Server referrer: Google (as provided by Cloudflare's proxy)
  • Client referrer: Untalent, with the cf parameter.

So, at the moment, there is one pageview counted, and since it is considered an internal link, it will not be counted as a new visit.

With the referral overwrite, the only difference is:

• Next page:
  • Client referrer: Google (overwritten).

I am not 100% sure about this, so please take it with a pinch of salt.

[adriaandotcom]

Compiled version: https://gist.github.com/adriaandotcom/bc456c1e046294c6ed8f51e9793351c4

[adriaandotcom]

Included in #40