feat(ske): add datasource to query provider options

[h3adex]

Description

This PR adds the ske options API as datasource to query kubernetes and machine versions. Currently the API does not support any filtering option, but this can be done in the meanwhile using terraform locals. Example code is in the generated docs.

data "stackit_ske_provider_options" "this" {}

locals {
  k8s_versions = [
    for v in data.stackit_ske_provider_options.this.kubernetes_versions :
    v.version if v.state == "supported"
  ]
  first_k8s_version = length(local.k8s_versions) > 0 ? local.k8s_versions[0] : ""
  last_k8s_version = length(local.k8s_versions) > 0 ? local.k8s_versions[length(local.k8s_versions) - 1] : ""


  flatcar_supported_versions = flatten([
    for mi in data.stackit_ske_provider_options.this.machine_images : [
      for v in mi.versions :
      v.version if mi.name == "flatcar" && v.state == "supported"
    ]
  ])

  ubuntu_supported_versions = flatten([
    for mi in data.stackit_ske_provider_options.this.machine_images : [
      for v in mi.versions :
      v.version if mi.name == "ubuntu" && v.state == "supported"
    ]
  ])
}

output "first_k8s_version" {
  value = local.first_k8s_version
}

output "last_k8s_version" {
  value = local.last_k8s_version
}

output "k8s_versions" {
  value = local.k8s_versions
}

output "ubuntu_supported_version" {
  value = local.ubuntu_supported_versions[0]
}

output "flatcar_supported_version" {
  value = local.flatcar_supported_versions[0]
}

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)

[hown3d]

Even if the API does not allow for filtering at the moment, we should still support filtering in the terraform go code.
Using locals may be possible, but is not a nice API and not something I want to recommend.

[hown3d]

Closes #953

[rubenhoenle]

The list provider options endpoint returns a lot of different information.

I wouldn't combine all of this into a single datasource, instead I would create multiple datasources here. (IMO there should be also multiple endpoints for listing k8s versions, listing machine types, ... but that's another discussion.)

So I would suggest

• datasource stackit_ske_kubernetes_versions
• datasource stackit_ske_machine_types
• datasource stackit_ske_volume_types
• ...