Improve Mimir/Metrics handbook documentation
We have recently migrated our Metrics stack over to Mimir. &1107 (closed) As part of this we have added basic operational guidelines to a runbook: https://gitlab.com/gitlab-com/runbooks/-/tree/master/docs/mimir?ref_type=heads
However, there is still fresh information that hasn't necessarily been written down. example The handbook is fairly sparse in regards to Mimir information - we should improve this is make knowledge more easily discoverable.
Update: This policy should be updated https://handbook.gitlab.com/handbook/engineering/gitlab-com/policies/monitoring/ to specify monitoring retention.
Edited by Liam McAndrew