Feature/cloud profile storage type

[hebelsan]

How to categorize this PR?

/area quality
/kind enhancement
/platform openstack

What this PR does / why we need it:
This PR adjusts the default values for the machineclass values rootDiskType and rootDiskSize.
These will now be derived from the cloudProfile machineType spec which looks the following:

spec:
  machineTypes:
  - architecture: amd64
    cpu: "4"
    gpu: "0"
    memory: 8Gi
    name: g_k_c4_m8_v2
    storage:
      class: standard
      size: "64"
      type: premium
    usable: true

If the storage section of the machineType is not set or the type is set to default the machinclass fields for rootDiskType and rootDiskSize will be empty so the openstack defaults will be used.
It's still possible to overwrite the default disk type and size by setting the shoot fields.

Which issue(s) this PR fixes:
Fixes #1316

Special notes for your reviewer:

Release note:

Behavioral change: rootDiskType and rootDiskSize now derived from cloud profile machine type storage.
Previously, if a worker pool did not explicitly configure volume.type / volume.size, the generated MachineClass omitted rootDiskType and rootDiskSize entirely, leaving the choice to OpenStack's infrastructure defaults.
With this change, if the cloud profile's MachineType.Storage defines a type (other than "default") and optionally a storageSize, those values are now used as defaults in the generated MachineClass.
Impact: Shoots using machine types whose cloud profile entry has a non-"default" Storage.Type will now have an explicit rootDiskType (and potentially rootDiskSize) set in their MachineClass. If this differs from the OpenStack infrastructure's previous default, the root disk type of newly created nodes will change.
Action required: Review the Storage field on machine types in affected cloud profiles. If the Storage.Type was set for informational purposes only and should not influence disk provisioning, set it to "default" to preserve the previous behavior.

[github-actions]

This change enhances the machine class configuration logic to automatically use storage specifications from cloud profiles when not explicitly set in shoot specifications, particularly beneficial for KVM machines requiring premium disk types for boot disks.

Walkthrough

• New Feature: Added automatic fallback to cloud profile machine type storage settings (type and size) when pool volume specifications are not provided in shoot configurations
• Chore: Updated .gitignore to exclude AI coding agent artifacts like Claude configuration files and skills lock files
• Test: Added comprehensive test coverage to verify that storage type and size are correctly inherited from cloud profile machine types when pool volumes are unspecified

The implementation includes proper validation to ensure storage types aren't "default" and handles storage size conversion with appropriate error checking. This enhancement improves the user experience by reducing required configuration while maintaining explicit control when needed.

_{Model: claude-sonnet-4-20250514 | Prompt Tokens: 1630 | Completion Tokens: 181}

[AndreasBurger]

/approve

[AndreasBurger]

since auto-merge is blocked by milestone anyways and this l's gtm I can actually properly approve this.

[gardener-prow]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: AndreasBurger

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• OWNERS [AndreasBurger]

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[gardener-prow]

LGTM label has been added.

Details

Git tree hash: ec5f681ff565bdf0c859a84fae48aee288b4f6ac