Feat/dns zone observability extension

[SerseusWasTaken]

Description

relates to #STACKITTPR-319 and closes #941

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)

[github-actions]

This PR was marked as stale after 7 days of inactivity and will be closed after another 7 days of further inactivity. If this PR should be kept open, just add a comment, remove the stale label or push new commits to it.

[marceljk]

When I create a dns_zone with observability enabled and remove the whole extension during an update, the terraform fails with an state drift.

resource "stackit_observability_instance" "observability" {
  project_id = var.project_id
  name       = "marcel-dns-test"
  plan_name  = "Observability-Metrics-Endpoint-100k-EU01"
}

resource "stackit_dns_zone" "dns_zone" {
  project_id    = var.project_id
  name          = "my-dns-zone"
  dns_name      = "tf-acc-a8d583413.stackit.gg"
  contact_email = "aa@bb.ccdd"
  type          = "primary"
  default_ttl   = 3600
  # Enable first the extension and remove it then for an update
  # extensions    = {
  #   observability = {
  #     observability_instance_id = stackit_observability_instance.observability.instance_id
  #   }
  # }
}

Error message:

╷
│ Error: Provider produced inconsistent result after apply
│ 
│ When applying changes to stackit_dns_zone.dns_zone, provider "provider[\"registry.terraform.io/stackitcloud/stackit\"]" produced an unexpected new value: .extensions: was null, but now
│ cty.ObjectVal(map[string]cty.Value{"observability":cty.ObjectVal(map[string]cty.Value{"observability_instance_id":cty.StringVal("be4a8756-09ff-4b93-a861-bfb4f84ab2bf"), "state":cty.StringVal("CREATING")})}).
│ 
│ This is a bug in the provider, which should be reported in the provider's own issue tracker.

[SerseusWasTaken]

When I create a dns_zone with observability enabled and remove the whole extension during an update, the terraform fails with an state drift.

resource "stackit_observability_instance" "observability" {
  project_id = var.project_id
  name       = "marcel-dns-test"
  plan_name  = "Observability-Metrics-Endpoint-100k-EU01"
}

resource "stackit_dns_zone" "dns_zone" {
  project_id    = var.project_id
  name          = "my-dns-zone"
  dns_name      = "tf-acc-a8d583413.stackit.gg"
  contact_email = "aa@bb.ccdd"
  type          = "primary"
  default_ttl   = 3600
  # Enable first the extension and remove it then for an update
  # extensions    = {
  #   observability = {
  #     observability_instance_id = stackit_observability_instance.observability.instance_id
  #   }
  # }
}

Error message:

╷
│ Error: Provider produced inconsistent result after apply
│ 
│ When applying changes to stackit_dns_zone.dns_zone, provider "provider[\"registry.terraform.io/stackitcloud/stackit\"]" produced an unexpected new value: .extensions: was null, but now
│ cty.ObjectVal(map[string]cty.Value{"observability":cty.ObjectVal(map[string]cty.Value{"observability_instance_id":cty.StringVal("be4a8756-09ff-4b93-a861-bfb4f84ab2bf"), "state":cty.StringVal("CREATING")})}).
│ 
│ This is a bug in the provider, which should be reported in the provider's own issue tracker.

State drift is fixed, but there seems to be a bug in the API which allows to link invalid observability instances. We will wait with this PR until the issue is addressed

[github-actions]

Merging this branch will increase overall coverage

Impacted Packages	Coverage Δ	🤖
github.com/stackitcloud/terraform-provider-stackit/stackit/internal/services/dns	0.00% (ø)
github.com/stackitcloud/terraform-provider-stackit/stackit/internal/services/dns/zone	21.78% (+3.22%)	👍

---

Coverage by file

Changed files (no unit tests)

Changed File	Coverage Δ	Total	Covered	Missed	🤖
github.com/stackitcloud/terraform-provider-stackit/stackit/internal/services/dns/zone/datasource.go	0.00% (ø)	64	0	64
github.com/stackitcloud/terraform-provider-stackit/stackit/internal/services/dns/zone/resource.go	27.10% (+3.31%)	262 (+35)	71 (+17)	191 (+18)	👍

Please note that the "Total", "Covered", and "Missed" counts above refer to code statements instead of lines of code. The value in brackets refers to the test coverage of that file in the old version of the code.

Changed unit test files

• github.com/stackitcloud/terraform-provider-stackit/stackit/internal/services/dns/dns_acc_test.go
• github.com/stackitcloud/terraform-provider-stackit/stackit/internal/services/dns/zone/resource_test.go