4.12.0

This minor release in the 4.x series adds the following improvements:

• RUBY-2397 Support parsing $uuid as extended JSON representation for subtype 4 binary
• RUBY-2504 Ensure return value of all BSON::Document methods is a BSON::Document instance potentially breaking change

The following bugs were fixed:

• RUBY-2438 to_uuid does not add the fourth dash to serialized uuid potentially breaking change
• RUBY-2487 BSON::Document#except does not exclude symbol arguments with ActiveSupport 6 potentially breaking change
• RUBY-2491 Repair BSON::Document#slice on Ruby 2.4 with ActiveSupport