feat: on_spot_discontinue on os_volume and delete_permanently on instance action

[huksley]

1. Support on_spot_discontinue on os volume when creating an instance. No check is implemented to avoid sending on_spot_discontinue if instance is not SPOT instance and API will fail on that.

verda.instances.create(
    hostname='test-instance',
    location=Locations.FIN_03,
    instance_type='CPU.4V.16G',
    description='test cpu instance',
    image='ubuntu-22.04',
    is_spot=True,
    ssh_key_ids=[ssh_key.id],
    os_volume=OSVolume(name='test-os-volume-spot', size=56, on_spot_discontinue='delete_permanently'),
)

Will call API with:

POST v1/instances
{
  "instance_type": "CPU.4V.16G",
  "image": "ubuntu-24.04",
  "ssh_key_ids": [ "442e6a59-26c2-4cea-a619-39762c0d2385" ],
  "hostname": "test-instance",
  "location_code": "FIN-03",
  "is_spot": true,
  "os_volume": {
    "name": "test-instance-os-volume",
    "size": 55,
    "on_spot_discontinue": "keep_detached" | "move_to_trash" | "delete_permanently" // <= If "delete_permanently", volume will be deleted when spot instance is automatically discontinued
  }
}

3. When deleting (discontinuing) the instance, allow to delete volumes permanently in one go. Add optional parameter to verda.instances.action():

verda.instances.action(
    instance.id, 'delete', volume_ids=[instance.os_volume_id], delete_permanently=True
)

Will call API:

PUT v1/instances
{
  "action": "delete",
  "id": "442e6a59-26c2-4cea-a619-39762c0d2385",
  "volume_ids": [ "5e9e63a9-fc3b-427b-b259-0c77dce61090" ],
  "delete_permanently": true // <= Will delete instance and volumes permantently
}

[Copilot]

Pull request overview

This PR adds support for managing volume lifecycle when working with spot instances and provides a way to permanently delete volumes when deleting instances.

Changes:

• Added OSVolume dataclass with on_spot_discontinue parameter to control volume behavior when spot instances are discontinued
• Added delete_permanently parameter to the action() method to allow permanent deletion of volumes in a single operation
• Updated integration tests to demonstrate the new features

Reviewed changes

Copilot reviewed 5 out of 5 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
verda/instances/_instances.py	Introduced OSVolume dataclass with on_spot_discontinue field and added delete_permanently parameter to action() method
verda/instances/init.py	Exported new OSVolume and OnSpotDiscontinue types
tests/unit_tests/instances/test_instances.py	Added unit tests for creating spot instances with OSVolume and for action() with delete_permanently
tests/integration_tests/test_spot_instances.py	Added integration test demonstrating spot instance creation with on_spot_discontinue set to delete_permanently
tests/integration_tests/test_instances.py	Updated integration test to use new delete_permanently parameter when deleting instances

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