Refactor zones

- Rename "zonefile_setting" to "zone"
- Remove version

#475

app/models/dns/zone.rb

@@ -0,0 +1,48 @@
+module DNS
+  class Zone < ActiveRecord::Base
+    validates :origin, :ttl, :refresh, :retry, :expire, :minimum_ttl, :email, :master_nameserver, presence: true
+    validates :ttl, :refresh, :retry, :expire, :minimum_ttl, numericality: { only_integer: true }
+    validates :origin, uniqueness: true
+
+    before_destroy :check_for_dependencies
+
+    def check_for_dependencies
+      dc = Domain.where("name ILIKE ?", "%.#{origin}").count
+      return if dc == 0
+      errors.add(:base, I18n.t('there_are_count_domains_in_this_zone', count: dc))
+      false
+    end
+
+    def self.generate_zonefiles
+      pluck(:origin).each do |origin|
+        generate_zonefile(origin)
+      end
+    end
+
+    def self.generate_zonefile(origin)
+      filename = "#{origin}.zone"
+
+      STDOUT << "#{Time.zone.now.utc} - Generating zonefile #{filename}\n"
+
+      zf = ActiveRecord::Base.connection.execute(
+        "select generate_zonefile('#{origin}')"
+      )[0]['generate_zonefile']
+
+      File.open("#{ENV['zonefile_export_dir']}/#{filename}", 'w') { |f| f.write(zf) }
+
+      STDOUT << "#{Time.zone.now.utc} - Successfully generated zonefile #{filename}\n"
+    end
+
+    def self.origins
+      pluck(:origin)
+    end
+
+    def to_s
+      origin
+    end
+
+    def to_partial_path
+      'zone'
+    end
+  end
+end