Update DTOs with additional fields

[mxsrc]

Chris noted that the API v2 DTOs are relatively sparse, this introduces additional fields (or identifies they have been added already. Fields that were renamed are commented, fields that have not been added have comments elaborating the reason:
ClusterDTO

• capacity_total_bytes (total available capacity bytes incl. erasure coding overhead)
  • capacity
• capacity_provisioned_bytes (provisioned bytes)
  • capacity
• capacity_used_bytes (actual used bytes)
  • capacity
• volumes_max (number of maximum allowed logical volumes)
  • Does not exist on cluster model
• snapshots_max (number of maximum allowed snapshots if this exists)
  • Does not exist on cluster model

StorageNodeDTO

• cluster_id
• status (exists, but would be nice to find the available status values in a literal)
• volumes_max (number of maximum allowed logical volumes in this storage node)
  • lvols_max for consistency
• capacity_total_bytes (total available capacity bytes incl. erasure coding overhead)
  • capacity
• capacity_provisioned_bytes (provisioned bytes)
  • capacity
• capacity_used_bytes (actual used bytes)
  • capacity
• snapshots_max (number of maximum allowed snapshots in this storage node)
• spdk_port
• hub_lvol_port
• hostname
• hugepages_bytes
  • hugepages
• cpu_total_count
• cpu_spdk_count
• cpu_poller_count
• cpu_xyz_count
• memory_bytes
  • memory
• host_nqn
• uptime

DeviceDTO

• cluster_device_order
• model (previously model_id)
• cluster_id
• storage_node_id
• nvme_controller
• pcie_address
• block_device_label (/dev/by-id/… when we have block device support)
  • not yet implemented
• retries_exhausted
• serial_number
• uptime
  • not available to the API

VolumeDTO

• crypto_key_name
  • unused field
• cluster_id
• storage_node_id
• io_error
• priority_class
• access_mode (previously mode)
• namespace_id (the nvme namespace id of this volume)
  • namespace

StoragePoolDTO

• cluster_id

ClusterTaskDTO: Actually cluster tasks API is completely missing on V2

• cancelled
• cluster_id
• device_id
• storage_node_id
• function_name
• function_params
• function_result
• max_retry
• retry
• status

StorageNodeLogs API missing

• Isn't that handled via graylog?