feat: Add support for GCP Secret Manager

[gr0]

Handles #108 and introduces the GCP Secret Manager to Chainloop. Allows the user to provide the project identifier and the key enabling access to the secret manager.

Any comments, suggestions, review is more than welcome :)

[migmartri]

@gr0 please rebase main to include this check too #126

Thanks!

[migmartri]

go mod tidy in this code will fails and this is the culprit #127

gRPC v1.55.0 is a dependency for the latest version of secretmanager which was added in this patch. The bad news is that kratos is not compatible with gRPC v1.55.0 yet go-kratos/kratos#2832 and the fix will be in the next release.

Until then my suggestion to move forward would be to keep back gRPC and secret manager

You can achieve that by running

$ go get google.golang.org/grpc@v1.54.0
go: downloading cloud.google.com/go/secretmanager v1.10.0
go: downgraded cloud.google.com/go/secretmanager v1.10.1 => v1.10.0
go: downgraded google.golang.org/grpc v1.55.0 => v1.54.0

I've created this other issue to tackle the upgrade when possible #127

[migmartri]

This is awesome! Thanks a lot for the contribution!

Note that you might notice that I am being more strict with this code than with the foundation that you've worked on top of.

That's right, I am not super proud with some of the code I wrote, and I'd love to improve it. Via both contributions like yours and also by my own contributions, for which I expect you to be strict with me too! :)

Thanks for your patience and great work!

Let me know if you want to chat over discord or smth if it simplifies, speeds up the review process! :)

[migmartri]

Looks good :), not approving modulo making sure the PK comment gets reviewed, see below.

[migmartri]

LGTM!

Thanks a lot for the contribution! 🎉