Grafana: Add new users

1. Enable sign ups temporarily
2. Ask users to sign up
3. Add new users to desired groups
4. Disable sign ups
   1. If you're asking why we do it like so, ask @Aleksandar Poposki

Automatic team assignment on sign up

Free, self-hosted Grafana does not have a feature to automatically assign a team when signing up. There is only a paid feature called Team Sync that uses your Identity Provider (IdP) to sync permissions from an external domain to Grafana.