Development docs: how to add Prometheus metrics
Development docs: how to add Prometheus metrics

This documents the various knowledge needed to add new GitLab
self-monitoring Prometheus metrics.

stoplightio/gitlabhq,stoplightio/gitlabhq,mmkassem/gitlabhq,stoplightio/gitlabhq,mmkassem/gitlabhq,mmkassem/gitlabhq,stoplightio/gitlabhq,mmkassem/gitlabhq