default hash algorithm changed in rails7

[nov]

The default hash algorithm used in ActiveSupport::KeyGenerator changed from SHA1 to SHA256.

It affects ActiveRecordEncryption::Encryptor::ActiveSupport and causes ActiveSupport::MessageVerifier::InvalidSignature when accessing to an attribute encrypted using SHA1.

[nov]

ps.
in our current app, key_generator uses SHA1 on the first load.
and once the app is reloaded (on development env), it changes the hash algorithm to SHA256.

[alpaca-tc]

@nov Sorry for the delay in replying.
If you have already fix this issue in your application, could you please send a PR?