Support AWS CodeCommit Access with IAM Role

[taraspos]

Summary

Support AWS CodeCommit auto-renewed credentials for IAM roles, similarly to what aws/git-remote-codecommit does.

Context

Original issue (#835) was closed due to AWS CodeCommit deprecation. However AWS recently announced that CodeCommit Returns to General Availability as such I would like to re-open this feature request.

[taraspos]

I took a look at implementing this, and found that AWS Go SDK Signer is incompatible with CodeCommit request signing:

• aws/signer/v4 is not compatible with CodeCommit request signing aws/aws-sdk-go-v2#3310

Workaround is to implement custom signer:

• https://github.com/gembaadvantage/codecommit-sign/blob/main/pkg/awsv4/signer.go

[matheuscscp]

This feature must be implemented here: https://github.com/fluxcd/pkg/tree/main/auth

We have support for Azure DevOps Git repositories, whatever we do for AWS CodeCommit has to fit in this library