* Users may have external CA setups that pre-configure certificates.
* The CaClient can use JWT token for the initial setup, then switch to mTLS certificates.

Note that `OUTPUT_CERTS` can be used to refresh certificates using previously provisioned certificates, by configuring
the ca client to use certificates written to the same directory we have configured them to be written to.

## Authentication

  repeated APIResourceDiscovery resources = 2;

  // freshness marks whether a group version's discovery document is up to date.
  // "Current" indicates the discovery document was recently
  // refreshed. "Stale" indicates the discovery document could not
  // be retrieved and the returned discovery document may be
  // significantly out of date. Clients that require the latest