Create snapshot API handlers

Goal

Implement a creating snapshot method for provisioning

TODO / How to implement

Wait for readiness the issue about refactoring the Retrieval service: #375 (closed)

TODO

• Add new methods to API
  • POST /snapshot/create - creates a new snapshot
    • use the SnapshotData method from the Retrieval service
    • should support the ability to specify a data pool (use the current active pool by default)
    • example of the request body

       {
          "poolName": "dblab_pool"
       }

  • POST /snapshot/delete - deletes the snapshot by name
    • use DestroySnapshot(string) error from the Snapshotter interface (FSManager)
    • example of the request body:

       {
          "snapshotID": "dblab_pool@snapshot_20220525010741"
       }

• CLI commands for new API handlers
  • dblab snapshot create / dblab snapshot create --pool dblab_pool
  • dblab snapshot delete dblab_pool@snapshot_20220525010741
• Add tests
• Describe changes (API, CLI, How-To) in the docs

Acceptance criteria

The user has the ability to create and delete a snapshot via API