Add some helpful jq commands to trawl through logs

it is especially useful to find on-disk files and package versions.

### Filtering through json logs

The most useful log to look into when trying to identify errors or traffic

patterns is `/var/log/gitlab-rails/production_json.log`. It shows all of the

activity on the web interface.

Since the file is formatted in JSON, to filter through this file, you need to

use `jq` to filter lines. Here are some useful examples that you can build upon

for your search:

To find requests that got a server error (e.g. 500 http status code) response:

    jq 'select(.status==500)' production_json.log

To get lines only from a defined period of time:

    jq --arg s '2024-07-16T07:10:00' --arg e '2024-07-16T07:19:59' 'select(.time | . >= $s and . <= $e + "z")' prodcution_json.log

To identify the individual IP addresses with the highest number of requests for

the day:

    jq -rC '.remote_ip' production_json.log | sort | uniq -c | sort -n | tail -10

### GitLab pages not found

If you're looking for a way to track GitLab pages error, know that the