Feat/implement advanced image search options

[h3adex]

Description

This PR improves the stackit_image_v2 data source by enabling image selection via name, regex, or detailed filters (OS, distro, version, UEFI, and secure_boot). When multiple results match (e.g., Ubuntu 18.04, 20.04...), they are sorted descending by name, selecting the newest. Similar to Azure’s behavior.

The design aligns with syntax and behavior from other providers like Azure, Google, and OpenStack.

Unlike Google/OpenStack, we avoid relying on most_recent or timestamps (created_at, updated_at) since these refer to upload/update events—not actual image creation by the vendor. Instead, we sort by name/system version to reliably select the latest version.

Code to test it:

variable "project_id" {}

data "stackit_image_v2" "name_match_ubuntu_22_04" {
  project_id = var.project_id
  name       = "Ubuntu 22.04"
}

data "stackit_image_v2" "ubuntu_by_image_id" {
  project_id = var.project_id
  image_id   = data.stackit_image.name_match_ubuntu_22_04.image_id
}

data "stackit_image_v2" "regex_match_ubuntu_22_04" {
  project_id = var.project_id
  name_regex = "(?i)^ubuntu 22.04$"
}

data "stackit_image_v2" "filter_debian_11" {
  project_id = var.project_id
  filter = {
    distro  = "debian"
    version = "11"
  }
}

data "stackit_image_v2" "filter_uefi_ubuntu" {
  project_id = var.project_id
  filter = {
    distro = "ubuntu"
    uefi = true
  }
}

data "stackit_image_v2" "name_regex_and_filter_rhel_9_1" {
  project_id = var.project_id
  name_regex = "^Red Hat Enterprise Linux 9.1$"
  filter = {
    distro = "rhel"
    version = "9.1"
    uefi = true
  }
}

data "stackit_image_v2" "name_windows_2022_standard" {
  project_id = var.project_id
  name       = "Windows Server 2022 Standard"
}

data "stackit_image_v2" "ubuntu_arm64_latest" {
  project_id = var.project_id
  filter = {
    distro = "ubuntu-arm64"
  }
}

data "stackit_image_v2" "ubuntu_arm64_oldest" {
  project_id = var.project_id
  filter = {
    distro = "ubuntu-arm64"
  }
  sort_ascending = true
}

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)

[h3adex]

E2E Tests

[Fyusel]

Looks good 😃 Only one nitpick