Add native support for other authentication mechanisms for ACM to connect to git repo

[grsiepka]

TL;DR

Using the ACM submodule, would like to see other options other than SSH key be available for ACM to use to authenticate to the backing git repo. My specific use case I'd like to see would be a gitlab token, but I'd imagine maybe there are others? I'm currently having to use a separate provider to populate the git-creds secret with my gitlab token, but it would be nice to have this feature natively in the ACM module

Terraform Resources

https://registry.terraform.io/modules/terraform-google-modules/kubernetes-engine/google/23.0.0/submodules/acm

Detailed design

maybe optional inputs for secrets to be provided like username/password/token etc?

Additional information

No response