feat(cli): onboard iaas snapshot api

[Benjosh95]

Description

Onboarding the snapshot API https://docs.api.stackit.cloud/documentation/iaas/version/v1#tag/Snapshots to manage the snapshot resources via the cli.

Checklist

• Issue was linked above
• Code format was applied: make fmt
• Examples were added / adjusted (see e.g. here)
• Docs are up-to-date: make generate-docs (will be checked by CI)
• Unit tests got implemented or updated
• Unit tests are passing: make test (will be checked by CI)
• No linter issues: make lint (will be checked by CI)

Testing-Instructions

1. Create a volume that will be used for snapshot testing.
   stackit volume create
   --availability-zone eu01-1
   --size 10
   --name "snapshot-test-vol"
   --labels purpose=snapshot-testing

2. Create a snapshot of the volume above

   • Required volume-id flag
   • Optional name and labels
   • Async operation
     stackit volume snapshot create
     --volume-id $VOLUME_ID
     --name "test-snap-1"
     --labels purpose=testing,test-type=minimal

3. List snapshot(s)
   stackit volume snapshot list --limit 3

4. Describe snapshot
   stackit volume snapshot describe $SNAPSHOT_ID

5. Update snapshot
   stackit volume snapshot update $SNAPSHOT_ID
   --name "test-snap-1-updated"
   --labels purpose=testing-updated

6. Verify update
   stackit volume snapshot describe $SNAPSHOT_ID

7. Delete the snapshot
   stackit volume snapshot delete $SNAPSHOT_ID

8. Delete the volume
   stackit volume delete $VOLUME_ID

[rubenhoenle]

Please check failing CI pipeline

[rubenhoenle]

• merge refactor(cli): add ConvertStringMapToInterfaceMap util function  #790 first and use the new util func here