ActiveSupport::MessageEncryptor' cipher option

[nalabjp]

The default cipher of ActiveSupport::MessageEncryptor changed in rails 5.2.
rails/rails#29263

If we are using the encryptor of ActiveRecordEncryption::Encryptor::ActiveSupport with aes-256-cbc in rails 5.1, raising the rails version to 5.2 will cause an error due to cipher changing to aes-256-gcm.

So, I think that we need to pass cipher options to the encryptor or directly specify the encryptor class with cipher.

@alpaca-tc
What do you think about this?