Add GSuite SSO to Grafana

Here's what I intend to happen:

1. The testing and production Grafana instances will not be accessible anonymously anymore, but instead require GSuite SSO authentication.
2. Grafana will not ask nor offer to create accounts, just as before. Anyone who is authenticated through GSuite will have admin level rights in Grafana, just like before any anonymous user was admin in Grafana.
3. The monitoring server will expose Grafana publicly via HTTPS.

Attention @jcalderone : I cannot test this currently since I don't have GSuite.

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• Solves privatestorageops#361.