Is there an existing issue for this?

• I have searched the existing issues

Current Behavior

It seems that Sign operation ignores MessageType.
As per AWS documentation the MessageType can be "DIGEST", that means the digest is already computed and just needs to be signed.
https://docs.aws.amazon.com/kms/latest/APIReference/API_Sign.html

Localstack ignores this parameter:

In GoLang the Sign interface takes the digest, not the raw message.
Sign(rand io.Reader, digest []byte, opts crypto.SignerOpts)
Therefore Sign/Verify operations in Go fail by using localstack.

Expected Behavior

Use MessageType parameter and do not compute the digest when MessageType==DIGEST

How are you starting LocalStack?

With a docker-compose file

Steps To Reproduce

Use Sign/Verify in GoLang

Environment

- OS: ubuntu
- LocalStack: latest
- GoLang 1.19

Anything else?

No response