Nomad autoscale_constraints improperly rendered with AWS Elastigroup

[jfcantu]

TL;DR - When integration_nomad {} is specified for an AWS Elastigroup, the provider doesn't properly translate autoscaler_constraints blocks into JSON for the API request.

Terraform Version

Terraform v0.12.21 (latest available in Chocolatey)

Provider versions:

• provider.aws v2.52.0
• provider.spotinst v1.14.2

Affected Resource(s)

• spotinst_elastigroup_aws

Terraform Configuration Files

Truncated to relevant section:

    integration_nomad {
        autoscale_constraints {
                key = "node.class"
                value = "test"
        }
    }

Actual Behavior

When Terraform displays the plan output, it shows the correct projected actions for the resource:

Truncated to relevant section:

+ integration_nomad {
    + autoscale_constraints {
        + key   = "${node.class}"
        + value = "test"
    }
}

However, the debug output shows improper JSON being sent to the API:

Truncated to relevant section:

"thirdPartiesIntegration": {
    "nomad": {
        "autoScale": {
            "constraints": [
            {
                "key": "${node.class}",
                "value": ""
            },
            {
                "key": "${${node.class}}",
                "value": "test"
            }
            ]
        }
    }
}

This results in a ValidationError being returned from the API:

[ERROR] failed to create group: POST https://api.spotinst.io/aws/ec2/group: 400 (request: "566d5d84-eac3-4e7d-8e6d-fa59d770594f") ValidationError: "value" is not allowed to be empty (field: body:group.thirdPartiesIntegration.nomad.autoScale.constraints.0.value)

Steps to Reproduce

1. Attempt to create a spotinst_elastigroup_aws resource that contains an autoscale_constraints{} block.

Important Factoids

This seems like this may have been introduced with Terraform 12. I have access to another configuration repository which uses TF11, and this issue does not occur.