WIP: Plugin server backpressure runbook

[yakkomajuri]

Changes

Super WIP, just giving visibility.

Things that still need doing (either now or later):

• Restructure the docs to determine where this should sit
• Adding dashboards/panels to the helm chart Grafana
• ...

Checklist

• [ ] Titles are in sentence case
• [ ] Feature names are in title case
• [ ] Words are spelled using American English
• [ ] I have checked out our style guide

[joethreepwood]

Converted to draft as this is listed as WIP and is quite old