fix(i18n): add Kosovo to countries list

Kosovo is not part of ISO 3166 as of time of writing. https://en.wikipedia.org/wiki/ISO_3166-2:RS#cite_ref-1

app/controllers/api/pays_controller.rb

@@ -2,7 +2,7 @@ class API::PaysController < ApplicationController
   before_action :authenticate_logged_user!
 
   def index
-    countries = I18nData.countries('FR').zip(I18nData.countries(I18n.locale))
+    countries = CountriesService.get('FR').zip(CountriesService.get(I18n.locale))
     countries = countries.map do |(code, value_fr), (localized_code, localized_value)|
       if code != localized_code
         raise "Countries lists mismatch. It means i18n_data gem has some internal inconsistencies."

app/models/champs/pays_champ.rb

@@ -20,7 +20,7 @@
 class Champs::PaysChamp < Champs::TextChamp
   def localized_value
     if external_id
-      I18nData.countries(I18n.locale)[external_id].to_s
+      CountriesService.get(I18n.locale)[external_id].to_s
     else
       value.present? ? value.to_s : ''
     end

app/services/countries_service.rb

@@ -0,0 +1,16 @@
+class CountriesService
+  def self.get(locale)
+    I18nData.countries(locale).merge(get_localized_additional_countries(locale))
+  end
+
+  def self.get_localized_additional_countries(locale)
+    additional_countries[locale.to_s.upcase] || {}
+  end
+
+  def self.additional_countries
+    {
+      'FR' => { 'XK' => 'Kosovo' },
+      'EN' => { 'XK' => 'Kosovo' }
+    }
+  end
+end