[datadog_dashboard_json] bugfix for template_variables and notify_list

[dashashifrina]

Fix unnecessary diffs for template_variables and notify_list in dashboard_json resource

Description

When using the datadog_dashboard_json resource, Terraform would show unnecessary diffs during plan/apply when template_variables or notify_list fields were not explicitly defined in the configuration. This was happening because Terraform was treating an undefined field differently from a field set to null.

Changes

Modified the prepResource function to:

• Remove template_variables from state comparison when it's null or undefined
• Remove notify_list from state comparison when it's null or undefined
• Only sort notify_list when it contains actual values

Testing

To verify this fix:

1. Create a dashboard_json resource without explicitly defining template_variables or notify_list:

resource "datadog_dashboard_json" "test" {
 dashboard = <<EOF
{
   "title":"Ordered Layout Dashboard",
   "description":"Created using the Datadog provider in Terraform",
   "layout_type": "ordered",
   "widgets": [],
}
EOF

2. Run terraform apply to create the dashboard

3. Run terraform plan - you should see no changes detected. Previously, this would show:

Terraform will perform the following actions:

  # datadog_dashboard_json.timeseries will be updated in-place
  ~ resource "datadog_dashboard_json" "test" {
      ~ dashboard               = jsonencode(
          ~ {
              - notify_list        = null
              - template_variables = null
                # (6 unchanged attributes hidden)
            }
        )
        id                      = "wcu-vpm-pye"
        # (2 unchanged attributes hidden)
    }

[dashashifrina]

ℹ️ This should only be done if notifyList is defined.