Document Grafana access for communities

[GeorgianaElena]

We need documentation about Grafana for our communities.

Minimal information

Such documentation should contain at least the following information:

• that this is a feature available only on dedicated clusters
• how a community champion can create a Grafana username using the invite link that 2i2c creates and shared with them (engineering facing docs https://infrastructure.2i2c.org/sre-guide/support/grafana-account/)
• how a community champion can give access to other users via invite links as well. I think multiple users can use the same link to register, but this should be checked
• any changes made to the JupyterHub dashboards directory will not be persisted
• A very big warning that at the moment there isn't any documentation about what each dashboard or panel represents and this is an upstream work in progress

Extra information

• we should also have a policy about whether or not they can create other dashboards in other directories

[jmunroe]

I've made a first pass at adding some documentation in #200.

Still need to

• verify what exactly gets sent to hub champion and take screenshots of the process to set up an account
• verify the procedure if there are multiple community hub champions -- can the same invite link be reused?
• decide if community champions should be allowed to create their own dashboards
  • although those dashboards should persist, those changes will not be backed up anywhere
  • we may want to instead encourage hub champions to contribute upstream to jupyterhub/grafana-dashboards so that improvements propagate to all communities