The `nomad volume deregister` command currently returns an error if the volume
has any claims, but in cases where the claims can't be dropped because of
plugin errors, providing a `-force` flag gives the operator an escape hatch.
If the volume has no allocations or if they are all terminal, this flag
deletes the volume from the state store, immediately and implicitly dropping
all claims without further CSI RPCs. Note that this will not also
unmount/detach the volume, which we'll make the responsibility of a separate
`nomad volume detach` command.
CSI plugins can require credentials for some publishing and
unpublishing workflow RPCs. Secrets are configured at the time of
volume registration, stored in the volume struct, and then passed
around as an opaque map by Nomad to the plugins.
* command/agent/csi_endpoint: support type filter in volumes & plugins
* command/agent/http: use /v1/volume/csi & /v1/plugin/csi
* api/csi: use /v1/volume/csi & /v1/plugin/csi
* api/nodes: use /v1/volume/csi & /v1/plugin/csi
* api/nodes: not /volumes/csi, just /volumes
* command/agent/csi_endpoint: fix ot parameter parsing
* api/allocations: GetTaskGroup finds the taskgroup struct
* command/node_status: display CSI volume names
* nomad/state/state_store: new CSIVolumesByNodeID
* nomad/state/iterator: new SliceIterator type implements memdb.ResultIterator
* nomad/csi_endpoint: deal with a slice of volumes
* nomad/state/state_store: CSIVolumesByNodeID return a SliceIterator
* nomad/structs/csi: CSIVolumeListRequest takes a NodeID
* nomad/csi_endpoint: use the return iterator
* command/agent/csi_endpoint: parse query params for CSIVolumes.List
* api/nodes: new CSIVolumes to list volumes by node
* command/node_status: use the new list endpoint to print volumes
* nomad/state/state_store: error messages consider the operator
* command/node_status: include the Provider
