feat: add region fact

- add fact that maps primary ip subnet to a region code
- defaults to 'lost' if there is no subnet to region mapping

site/profiles/lib/facter/region.rb

@@ -0,0 +1,28 @@
+# frozen_string_literal: true
+
+# set region based on the subnet
+
+Facter.add('region') do
+  setcode do
+    # use facts['networking']['ip']to find the promary IP address
+    ip = Facter.value(:networking)['ip']
+
+    # subnet to region mapping
+    subnet_to_region = {
+      '198.18.17.0/24' => 'au-drw-1'
+    }
+
+    require 'ipaddr'
+
+    # Find the region for the IP
+    region = 'lost' # default to 'lost' if no region matches
+    subnet_to_region.each do |subnet, region_name|
+      if IPAddr.new(subnet).include?(IPAddr.new(ip))
+        region = region_name
+        break
+      end
+    end
+
+    region
+  end
+end