[BB-843] - Adding OIDC auth configuration items + Docs

Adding example layout of ODIC auth configuration to chart/values.yaml Adding KEYCLOAK.md to docs/ folder that explains all options that are required in addition to secret that is required to complete configuration.

Based off of existing instruction from upstream https://github.com/grafana/helm-charts/blob/main/charts/grafana/README.md#how-to-securely-reference-secrets-in-grafanaini