The `grafana_ldap_root_ca_cert` can be used to set the path to the root
CA certificate (bundle) Grafana uses to validate the certificate
presented by the configured LDAP server. By default, Grafana uses the
system root CA trust store, but this variable can be used in situations
where this is not suitable.
This commit introduces the *grafana* role and the corresponding
`grafana.yml` playbook. The role installs Grafana using the system
package manager, and configures the server (including LDAP
authentication).
