1) As a PMM User, I need to be able to add global annotations to PMM by  running pmm-admin annotate command  so that I can see Grafana annotation on all dashboards in PMM  (excl. QAN )

We expect no changes in Grafana dashboards (they were done in 2.0.0).

Example:

pmm-admin annotate "Upgrade to v1.2" --tags "UX,v1.2"

DOD:

Annotations added via CLI or API should be visible in grafana.
All annotations added globally should have extra tag `pmm_annotations`.

Out of scope:

• Removing and Updating existing annotations. 
• We don't save any data about annotations in pmm-managed.
• Grafana UI part

Suggested implementation:

1. New endpoint in pmm-managed API
2. Create grafana annotation  vi API (https://grafana.com/docs/grafana/latest/http_api/annotations/)

DOC: Level of documentation - same as we had for pmm1 - mention this in doc. LAter will go to the reference manual