fix(observability/alertgroup): for_each

[mitterle-sit]

Description

Using for_each with the stackit_observability_alertgroup broke with the version v0.81.0.

Error:

Error: Value Conversion Error
│ 
│   with stackit_observability_alertgroup.alert_rule_debug,
│ An unexpected error was encountered trying to build a value. This is always an error in the provider. Please report the following to the provider developer:
│ 
│ Received unknown value, however the target type cannot handle unknown values. Use the corresponding `types` package type or a custom type that handles unknown values.
│ 
│ Path: 
│ Target Type: []alertgroup.rule
│ Suggested Type: basetypes.ListValue`

OpenTofu:
OpenTofu v1.11.5
on darwin_arm64

Example:

resource "stackit_observability_instance" "test" {
  name       = "test"
  plan_name  = "Observability-Starter-EU01"
  project_id = "xxxx"
}

locals {
  alert_rule = {
    example1 = {
      name     = "debug-alert-group"
      interval = "60s"
      rules = [
        {
          alert      = "debug-alert-name"
          expression = "kube_node_status_condition{condition=\"Ready\", status=\"false\"} > 0"
          for        = "60s"
          labels = {
            severity = "critical"
          },
          annotations = {
            summary : "example summary"
            description : "example description"
          }
        },
        {
          expression = "kube_node_status_condition{condition=\"Ready\", status=\"false\"} > 0"
          labels = {
            severity = "critical"
          },
          record = "abc"
        },
      ]
    }
  }

}

resource "stackit_observability_alertgroup" "alert_rule_debug" {
  for_each    = local.alert_rule
  instance_id = stackit_observability_instance.test.instance_id
  name        = each.value.name
  project_id  = "xxx"
  rules       = each.value.rules
  interval    = each.value.interval
}

Checklist

• Issue was linked above
• Code format was applied: make fmt
• Examples were added / adjusted (see examples/ directory)
• Docs are up-to-date: make generate-docs (will be checked by CI)
• Unit tests got implemented or updated
• Acceptance tests got implemented or updated (see e.g. here)
• Unit tests are passing: make test (will be checked by CI)
• No linter issues: make lint (will be checked by CI)