Add Couchbase Server SSO (SAML) Management

Adding as a placeholder for future consideration

Server 7.6 adds SAML-based SSO, for the UI only (authenticating gives zero access to any CLI or REST endpoint).

As this has limited use in a Kubernetes environment, and is a one-off set-up task for anyone who does need it, this one can wait until we have sufficient demand and/or more flexible SSO methods added to Server.