[FR] Add support for cross project NEGs in net-lb-app-int module

[avh01]

Affected components

• Fabric modules
• FAST
• Blueprints
• Other

The problem

The resource google_compute_region_network_endpoint_group references var.project_id and it does not allow for the NEG to be created in a separate project. This issue and fix are very similar with ##3215 and is for the net-lb-app-int module instead. I can submit a merge request.

Release version

b5cc01c

Terraform version

Terraform v1.11

Steps to reproduce

Create an Internal App Load Balancer in one project and the NEG in a VPC that exists on a different project.

Expected behavior

I would expect the NEG to accept a different project ID.

Actual behavior

Terraform apply fails because it cannot find the VPC in the project where the LB is created since is on a different project.

Additional context

The fix:

[avh01]

The pull request has been submitted, I'm not sure if I need to assign someone as a reviewer #3286

[ludoo]

Pull request looks good, can you add an example to the README so the change is tested?