feat: add admin contact ident type validation

- Add new setting for allowed admin contact ident types
- Add validation for admin contact ident types on domain create/update
- Add UI controls for managing allowed ident types
- Add tests for new validation rules
- Update domain model to respect new settings

The changes allow configuring which identification types (private person,
organization, birthday) are allowed for administrative contacts. This is
enforced when creating new domains or adding new admin contacts.

app/controllers/admin/settings_controller.rb

@@ -27,12 +27,25 @@ module Admin
 
     def casted_settings
       settings = {}
-
+    
       params[:settings].each do |k, v|
-        settings[k] = { value: v }
+        setting = SettingEntry.find(k)
+        value = if setting.format == 'array'
+          processed_hash = available_options.each_with_object({}) do |option, hash|
+            hash[option] = (v[option] == "true")
+          end
+          processed_hash.to_json
+        else
+          v
+        end
+        settings[k] = { value: value }
       end
-
+    
       settings
     end
+    
+    def available_options
+      %w[birthday priv org]
+    end
   end
 end