feat: introduce emulation for sc, pv and pvc

[stevensbkang]

Closes #12.

Implementation Details

In Kubernetes, Storage Class, Persistent Volume Claim, and Persistent Volume are generally used for storage. Translating these to the Docker terms:

• Storage Class = Volume Plugins
  • This can be expanded to other plugins, such as CSI drivers, in future
• Persistent Volume Claim = N/A
• Persistent Volume = Docker Volume

Unlike Kubernetes, where a storage class can be defined as a manifest, creating a Volume plugin on demand is impossible at the Docker layer. Hence, only the GET and LIST operations will be added, defaulting to the local Docker Volume driver only as a starting point.

Since there is no concept of Persistent Volume Claim in Docker, the decision was to merge PV and PVC into Docker Volume. This means that the creation and deletion of a Docker Volume are only activated via PVC (dynamic PV creation). The user will not be able to create a PV and statically map it to a PVC. Rather, you can rely on the PVC to dynamically provision a PV, which is a Docker Volume in the backend.

Due to Docker Volume's immutable nature, for instance, updating its labels requires a complete recreation; the reclaim policy is set to Delete. There is a separate discussion to change the default policy to Retain.

The details of PVC are stored as a Docker Volume label, and PV is directly obtained from the specification of a Docker Volume.

Finally, mounting a PVC to a pod is equivalent to a Docker volume mount; docker run -v ${DOCKER_VOLUME}:/${PATH}.

[deviantony]

First initial review