Don't record unknown url params that don't come from our app. This
includes typos, url params from userscripts, and weird params from
broken bots, crawlers, or other unknown sources. Indexing too many
params can lead to a mapping explosion.
https://www.elastic.co/guide/en/elasticsearch/reference/current/mapping.html
Parse the user agent and log whether it seems like a known bot or a
human to NewRelic under the `user.bot` request attribute. This is so
that known bots can be filtered out of search traffic analytics. Bots
and search crawlers make up a significant portion of search traffic.
Log the Referer header, as well as the Sec-Fetch-* headers. These are
only sent by recent versions of Chrome; see https://www.w3.org/TR/fetch-metadata.
* Simplify code.
* Show backtraces for all users, not just builders.
* Show backtraces only for unexpected server errors (status 5xx), not
for normal client errors (status 4xx).
* Log expected errors at info level (reduce noise in production logs).
