Fix compatibility with Ruby 3.1' Psych version

The new Psych version required by Ruby 3.1 no longer allows the loading
of arbitrary classes into YAML by default. We switch to `#safe_load` and
enable the class we're currently using.

See:

ruby/psych@cb50aa8
ruby/psych@1764942

[skip ci]

core/app/models/spree/log_entry.rb

@@ -5,7 +5,7 @@ class LogEntry < Spree::Base
     belongs_to :source, polymorphic: true, optional: true
 
     def parsed_details
-      @details ||= YAML.load(details)
+      @details ||= YAML.safe_load(details, permitted_classes: [ActiveMerchant::Billing::Response])
     end
   end
 end