Switch nginx to use njs for IP anonymization

[cdrini]

Problem

Our nginx logs are no longer being formatted correctly -- although IPs are still anonymized. We have to switch to nginx with the njs modules from IA.

Related (possibly need new issues):

• nginx log backups aren't working
• Graph on homepage for unique visitor counts is 0 (likely because backup isn't working)

Breakdown

Requirements Checklist

• [ ]

Related files

• https://git.archive.org/ia/petabox/-/blob/2e2117725827b5e0d00498139073aad7fa6a16fb/etc/nginx/logging.js
• https://git.archive.org/ia/petabox/-/blob/2e2117725827b5e0d00498139073aad7fa6a16fb/etc/nginx/logging.conf#L2-3

Stakeholders

@scottbarnes

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