Enable the user to configure SMTP for Grafana (to enable email alerts)

[RobertLucian]

Description

This can be configured in the cluster config and updated while the cluster is running.

The best way to do this is to create a secret resource that will hold the user's credentials and then mount that as environment variables into the Grafana deployment.

Notes

• https://community.grafana.com/t/smtp-configuration-for-docker-container/16370
• https://grafana.com/docs/grafana/next/administration/configuration/