Cache default country for an hour

The default country usually never changes after the initial setup of an
instance.

app/models/spree/country.rb

@@ -6,6 +6,12 @@ module Spree
 
     validates :name, :iso_name, presence: true
 
+    def self.cached_find_by(attrs)
+      Rails.cache.fetch("countries/#{attrs.hash}", expires_in: 1.hour) do
+        find_by(attrs)
+      end
+    end
+
     def <=>(other)
       name <=> other.name
     end

app/services/default_country.rb

@@ -10,6 +10,6 @@ class DefaultCountry
   end
 
   def self.country
-    Spree::Country.find_by(iso: ENV["DEFAULT_COUNTRY_CODE"]) || Spree::Country.first
+    Spree::Country.cached_find_by(iso: ENV["DEFAULT_COUNTRY_CODE"]) || Spree::Country.first
   end
 end