High Availability capability additions for Grafana

From the initial investigation done in #81 (closed)

• a persistent database must be used or auth tokens are lost as users pass between pods

  • https://grafana.com/docs/grafana/latest/setup-grafana/set-up-for-high-availability/
  • https://grafana.com/docs/grafana/v9.0/setup-grafana/configure-grafana/#database

• Test with external or separate in-cluster postgres enabled and grafana.grafana.ini overrides set to point to postgres installation

• Grafana with multiple replicas allowing SSO login & dashboards + loki logs loading

• update HA section of arch doc and recommend using external Database for HA : ~/bigbang/docs/understanding-bigbang/package-architecture/monitoring.md with recommended values for running Grafana in HA