Adding A4X and Future NPI Support to JBVM

[LAVEEN]

This PR adds support for the gpu_topology attribute within the placement_policy for VM instances. This is necessary to support the upcoming A4x GPUs, which require a specific GPU topology to be defined for optimal performance.

[bytetwin]

With the new type check, the validation blocks are not needed. The type checking will ensure the placement_policy is either null or a map of provided keys with each value of the specified type.

Please ensure that this type validation is working on terraform version 1.5.7 (the ctk supported version). You can remove the valdiation blocks after testing to ensure that wrong values are flagged by the type checker

[cboneti]

/gemini review

[gemini-code-assist]

Code Review

This pull request adds support for the gpu_topology attribute in the placement_policy for VM instances. The changes are well-structured, including updates to the main Terraform logic, variable definitions, and documentation. I've provided a few suggestions to improve documentation accuracy, code style, and validation logic.

[gemini-code-assist]

The documentation for placement_policy has some issues:

1. The HTML line break tags are incorrect (</br>). They should be <br/>.
2. The list of supported fields is not very readable. Using a list format would improve clarity.
3. The type column is still any, but it has been updated to a specific object type in variables.tf. The documentation should reflect this change, which may require regenerating the documentation.

Suggested change

| <a name="input_placement_policy"></a> [placement\_policy](#input\_placement\_policy) | Control where your VM instances are physically located relative to each other within a zone.<br/>See https://registry.terraform.io/providers/hashicorp/google/latest/docs/resources/compute_resource_policy#nested_group_placement_policy<br/><br/>Supported fields:<br/> vm_count (number) </br> availability_domain_count (number)</br> collocation (string), max_distance (number)</br> gpu_topology (string). | `any` | `null` | no |

| <a name="input_placement_policy"></a> [placement\_policy](#input\_placement\_policy) | Control where your VM instances are physically located relative to each other within a zone.<br/>See https://registry.terraform.io/providers/hashicorp/google/latest/docs/resources/compute_resource_policy#nested_group_placement_policy<br/><br/>Supported fields:<ul><li>`vm_count` (number)</li><li>`availability_domain_count` (number)</li><li>`collocation` (string)</li><li>`max_distance` (number)</li><li>`gpu_topology` (string)</li></ul> | <pre>object({<br/> vm_count = optional(number)<br/> availability_domain_count = optional(number)<br/> collocation = optional(string)<br/> max_distance = optional(number)<br/> gpu_topology = optional(string)<br/> })</pre> | `null` | no |

[gemini-code-assist]

There is a trailing whitespace at the end of this line. Please remove it to maintain code style consistency.

    gpu_topology              = try(var.placement_policy.gpu_topology, "")

[gemini-code-assist]

Since you've changed the type of placement_policy from any to a specific object, this validation block can be improved. The current condition doesn't prevent providing an empty object (e.g., {}), which would cause a failure at apply time because google_compute_resource_policy requires at least one argument in group_placement_policy. A better validation would ensure that if placement_policy is provided, it contains at least one non-null value.

  validation {
    condition     = var.placement_policy == null || length([for v in values(var.placement_policy) : v if v != null]) > 0
    error_message = <<-EOT
    The var.placement_policy should be either unset/null or be an object with at least one non-null field. Supported fields are: vm_count, availability_domain_count, collocation, max_distance, gpu_topology.
    EOT
  }