Add metrics to monitor activity
- Add timing/count of api calls
- Add statistics on indexation
It uses statsd as it's not easy to use the prometheus client library on gunicorn server due to the multi-process management
https://github.com/prometheus/client_python#multiprocess-mode-gunicorn
Related to swh/infra/sysadm-environment#3042 (closed)
Migrated from D5103 (view on Phabricator)