Fix rails 7 deprecation on ActiveRecord::Base.default_timezone

Rails 7 added ActiveRecord.default_timezone and 7.1 will remove it from ActiveRecord::Base.

Extract a memoized method to hide this logic.

lib/inventory_refresh/save_collection/saver/base.rb

@@ -272,13 +272,18 @@ def assert_referential_integrity(hash)
       # @return [Time] A rails friendly time getting config from ActiveRecord::Base.default_timezone (can be :local
       #         or :utc)
       def time_now
-        if ActiveRecord::Base.default_timezone == :utc
+        if default_timezone_utc?
           Time.now.utc
         else
           Time.zone.now
         end
       end
 
+      def default_timezone_utc?
+        # Rails 7 added ActiveRecord.default_timezone and 7.1 will remove it from ActiveRecord::Base
+        @default_timezone_utc ||= (ActiveRecord.respond_to?(:default_timezone) ? ActiveRecord.default_timezone : ActiveRecord::Base.default_timezone) == :utc
+      end
+
       # Enriches data hash with timestamp columns
       #
       # @param hash [Hash] data hash