[api-ref] Add missing fields to the API Reference

Adding the 'service_uuid' and 'shared_targets' to the API Reference
documentation with a short description.

Closes-Bug: #1739640
Change-Id: I6866a8da47c6910ce8d2a6802839e9a06eb596a5

api-ref/source/v3/parameters.yaml

@@ -2371,12 +2371,26 @@ service_status:
   in: body
   required: true
   type: string
+service_uuid:
+  description: |
+    A unique identifier that's used to indicate what node the volume-service
+    for a particular volume is being serviced by.
+  in: body
+  required: true
+  type: string
 services:
   description: |
     A list of service objects.
   in: body
   required: true
   type: array
+shared_targets:
+  description: |
+    An indicator whether the back-end hosting the volume utilizes
+    shared_targets or not. Default=True.
+  in: body
+  required: true
+  type: boolean
 size:
   description: |
     The size of the volume, in gibibytes (GiB).

api-ref/source/v3/volumes-v3-volumes.inc

@@ -347,7 +347,8 @@ Response Parameters
    - created_at: created_at
    - os-volume-replication:driver_data: os-volume-replication:driver_data
    - volume_type: volume_type
-
+   - service_uuid: service_uuid
+   - shared_targets: shared_targets
 
 
 Response Example