stackit_ske_cluster: Changing Nodepool OS causes "Provider produced inconsistent result after apply"

[DerPozzi]

Description

Changing the Nodepool OS from flatcar to ubuntu causes tofu apply to fail with a provider consistency error.

Steps to reproduce

Run tofu apply

resource "stackit_ske_cluster" "example" {
  project_id = local.project_id
  name       = "example1"
  node_pools = [
    {
      name               = "np-example"
      machine_type       = "c1a.2d"
      os_name            = "ubuntu" #changed from 'flatcar' 
      minimum            = "1"
      maximum            = "2"
      availability_zones = ["eu01-1", "eu01-3"]
      volume_type        = "storage_premium_perf2"
      volume_size        = "60"
    }
  ]
  maintenance = {
    enable_kubernetes_version_updates    = true
    enable_machine_image_version_updates = true
    start                                = "01:00:00Z"
    end                                  = "02:00:00Z"
  }
}

1. Run terraform ...

Actual behavior

Expected behavior

Changing the OS of a Nodepool shouldn't return an inconsistent result.
It should return successfully after applying.

Environment

• OS: WSL - Arch
• OpenTofu version: v1.12.1
• Version of the STACKIT Terraform provider: `v0.90.0

Additional information

Feel free to add any additional information here.

The OS seems to be updated when checking in the Dashboard.