roles/grafana: Deploy Grafana

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).

group_vars/grafana/main.yml

@@ -0,0 +1,17 @@
+grafana_ldap_enabled: true
+grafana_http_addr: '[::1]'
+grafana_ldap_host: dc0.pyrocufflink.blue
+grafana_ldap_ssl: true
+grafana_ldap_start_tls: true
+grafana_ldap_bind_dn: CN=svc.grafana,CN=Users,DC=pyrocufflink,DC=blue
+grafana_ldap_search_filter: (sAMAccountName=%s)
+grafana_ldap_search_base_dns:
+- DC=pyrocufflink,DC=blue
+grafana_ldap_attr_username: sAMAccountName
+grafana_ldap_attr_email: mail
+grafana_ldap_group_mappings:
+- group_dn: CN=Grafana Admins,CN=Users,DC=pyrocufflink,DC=blue
+  org_role: Admin
+  grafana_admin: true
+- group_dn: '*'
+  org_role: Viewer