fix(iaas): remove UseStateForUnknown in network_interface and volume resource

[marceljk]

Description

relates to SSD3RD-11683

Testing instructions

1. Verify first the existing issue. Checkout the main branch and run $ make build
2. Use the following Terraform config and run it with $ terraform apply -var="env_stage=v1"

# ==============================================================================
# TERRAFORM CONFIGURATION
# ==============================================================================
terraform {
  required_providers {
    stackit = {
      source = "stackitcloud/stackit"
    }
    tls = {
      source  = "hashicorp/tls"
      version = ">= 4.0.0"
    }
  }
}


provider "stackit" {
  default_region = "eu01"
}


# ==============================================================================
# TERMINAL CONTROL VARIABLE
# ==============================================================================
variable "env_stage" {
  type        = string
  description = "Version tag that triggers the change scenario (e.g., v1, v2)"
  default     = "v1"
}


variable "project_id" {
  type    = string
  default = "" # TODO set to your project ID
}


variable "image_id" {
  type    = string
  default = "d333affd-9f00-446d-978f-524cb0384360"
}


# ==============================================================================
# DYNAMIC CONFIGURATION MAP (All Changes Are Managed Here)
# ==============================================================================
locals {
  # All names change dynamically based on the "env_stage" parameter provided from the terminal:
  cfg = {
    # --- RENAME & RECREATE GROUP ---
    server_name          = "jumphost-server-${var.env_stage}"
    keypair_name         = "jumphost-keypair-${var.env_stage}"
    update_schedule_name = "update-schedule-${var.env_stage}"


    # --- MODIFICATIONS ONLY GROUP ---
    sg_description   = "Jumphost SG Description ${var.env_stage}"
    volume_label_env = "poc-${var.env_stage}"
  }
}


# ==============================================================================
# REPRODUCED RESOURCES
# ==============================================================================


# 1. Modifications Only: Security Group
resource "stackit_security_group" "jumphost_sg" {
  project_id  = var.project_id
  name        = "vedat-poc-25152.jumphost-sg"
  description = local.cfg.sg_description # Modification Trigger
}


# 2. Network & Modifications Only: Network Interface
resource "stackit_network" "this" {
  project_id       = var.project_id
  name             = "vedat-poc-25152.poc-network"
  ipv4_nameservers = ["1.1.1.1"]
  ipv4_prefix      = "192.168.10.0/24"
  routed           = true
}


resource "stackit_network_interface" "this" {
  count              = 1
  project_id         = var.project_id
  network_id         = stackit_network.this.network_id
  security_group_ids = [stackit_security_group.jumphost_sg.security_group_id]

  labels = {
    environment = local.cfg.volume_label_env # Modification Trigger (Label Change)
    managed_by  = "terraform"
  }
}

# 3. Rename/Recreate: Key Pair
resource "tls_private_key" "generated_key" {
  algorithm = "RSA"
  rsa_bits  = 2048
}


resource "stackit_key_pair" "jumphost_keypair" {
  name       = local.cfg.keypair_name # Rename Trigger
  public_key = chomp(tls_private_key.generated_key.public_key_openssh)
}


# 4. Modifications Only: Volumes (Boot & Persistent)
resource "stackit_volume" "boot" {
  count             = 1
  project_id        = var.project_id
  name              = "vedat-poc-25152.boot-volume"
  size              = 20
  availability_zone = "eu01-1"


  labels = {
    environment = local.cfg.volume_label_env # Modification Trigger (Label Change)
    managed_by  = "terraform"
  }


  source = {
    type = "image"
    id   = var.image_id
  }
}


resource "stackit_volume" "jumphost_persistent_volume" {
  project_id        = var.project_id
  name              = "vedat-poc-25152.persistent-volume"
  size              = 10
  availability_zone = "eu01-1"


  labels = {
    environment = local.cfg.volume_label_env # Modification Trigger (Label Change)
    type        = "persistent"
  }
}


# 5. Rename/Recreate: Target Server
resource "stackit_server" "this" {
  project_id        = var.project_id
  name              = local.cfg.server_name # Rename Trigger
  machine_type      = "c2i.1"
  availability_zone = "eu01-1"
  keypair_name      = stackit_key_pair.jumphost_keypair.name


  boot_volume = {
    source_type = "volume"
    source_id   = stackit_volume.boot[0].volume_id
  }


  network_interfaces = [
    stackit_network_interface.this[0].network_interface_id
  ]
}


# 6. Rename/Recreate: Volume Attachment
resource "stackit_server_volume_attach" "jumphost_persistent_volume_attachment" {
  project_id = var.project_id
  server_id  = stackit_server.this.server_id
  volume_id  = stackit_volume.jumphost_persistent_volume.volume_id
}

3. After the apply run it again but set v2 for env_stage: $ terraform apply -var="env_stage=v2"
4. The apply will stop with 3 errors. All of them say that the provider produces inconsistent result after apply.
5. Run again $ terraform apply -var="env_stage=v2", to finish the open updates
6. Checkout this PR and run $ make build
7. Run now again an apply but set v3 for env_stage: $ terraform apply -var="env_stage=v3"
8. This time the apply should be successful on the first run.
9. Run $ terraform destroy to clean up the resources

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)