roles/named: Support managing zones

The *named* role now supports generating configuration for authoritative
DNS zones and DNSSEC keys. Zones are defined by populating the
`named_zones` variable with a list of objects describing the zone. Zone
properties can include:

* `name`: The DNS domain name
* `type`: The zone type, defaults to `master`
* `allow_update`: A list of hosts/networks or DNSSEC key names (which
  must be specified as an object with a `key` property)
* `update_policy`: A list of BIND update policy statements
* `ttl`: The default (minimum) TTL for the zone
* `origin`: The authoritative name server for the zone
* `refresh`, `retry`, `expire`: Record cache timeout values
* `default_records`: A list of default records, defined as objects with
  the following properties:
  * `name`: The RR name
  * `type`: The RR type (default: `A`)
  * `value`: The RR value

Zone files will be created in `/var/named/dynamic`. Existing zone files
will **not** be overwritten; management of zone records is done using
`nsupdate` or similar.

roles/named/tasks/main.yml

@@ -13,6 +13,26 @@
   tags:
   - install
 
+- name: ensure zones are configured
+  template:
+    src: named.zones.j2
+    dest: /etc/named.zones
+    mode: '0640'
+    owner: root
+    group: named
+    validate: named-checkconf %s
+  notify: reload named
+- name: ensure zone files exist
+  template:
+    src: zone.j2
+    dest: /var/named/dynamic/{{ item.zone }}.zone
+    mode: '0640'
+    owner: root
+    group: named
+    force: no
+  with_items: '{{ named_zones }}'
+  notify: reload named
+
 - name: ensure named is configured
   template:
     src: named.conf.j2