Roll out full IAM interface to artifact registry module

[NitriKx]

Describe the bug

The current implementation of the artifact-registry module is using an iam_binding resource to set the permissions, which is dropping any IAM permissions that has been set by another module.

Environment

Terraform v1.7.4
on darwin_arm64

c2780fa

To Reproduce

1. Create a repository using the artifact-registry module in a Terraform module A. Add some IAM permissions on the repository (service account for instance)
2. In a second Terraform module B, add some permissions to the repository (to add the service agent of another project to read artifacts)
3. Apply again the Terraform module A.

Expected behavior
The permissions set by the Terraform module B should be kept, alongside the one set by the module A

Result
The permissions set by the Terraform module B are dropped when applying the module A

Additional context
More insights on my current use case: I'm creating a Terraform module that creates a Virtual repository, but also creates the permissions in the remote GCP projects where the upstream repositories live.
In that context I have permissions set at:

1. at the creation of the upstream repository (allow some service accounts for the CI)
2. at the creation of the virtual repository

[ludoo]

The IAM interface used across all our modules supports both authoritative and additive bindings. Artifact registry is the exception and has never been updated to the new interface. I changed the title to reflect what actually needs to be done.

[NitriKx]

I've opened this PR, please let me know if that was the right way to implement the new interface

[juliocc]

Ah sorry, we basically did the same thing. I'll close mine.

[ludoo]

This has been merged, closing this (and thanks for flagging and taking care of it).