Stop logging the referer header

We originally logged this in order to help us separate malicious
traffic. Ultimately we've never ended up using this at all. As we're
reviewing our privacy policies, this seems like a good time to stop
logging things we don't care about that expose additional information
about our users.

Author: sgrif

src/middleware/log_request.rs

@@ -1,5 +1,5 @@
 //! Log all requests in a format similar to Heroku's router, but with additional
-//! information that we care about like User-Agent and Referer
+//! information that we care about like User-Agent
 
 use super::prelude::*;
 use crate::util::request_header;
@@ -34,14 +34,13 @@ impl Handler for LogRequests {
         print!(
             "at={level} method={method} path=\"{path}\" \
              request_id={request_id} fwd=\"{ip}\" service={time_ms}ms \
-             status={status} user_agent=\"{user_agent}\" referer=\"{referer}\"",
+             status={status} user_agent=\"{user_agent}\"",
             level = level,
             method = req.method(),
             path = FullPath(req),
             ip = request_header(req, "X-Real-Ip"),
             time_ms = response_time,
             user_agent = request_header(req, "User-Agent"),
-            referer = request_header(req, "Referer"), // sic
             request_id = request_header(req, "X-Request-Id"),
             status = response_code,
         );