Add v3 api-ref for updating snapshot status

This patch adds v3 api-ref for updating relative fields to status of a snapshot.

Change-Id: I24b8a05c814eb6a69ce957c75b8d168576774380

api-ref/source/v3/parameters.yaml

@@ -2059,6 +2059,12 @@ os-unset_image_metadata:
   in: body
   required: true
   type: object
+os-update_snapshot_status:
+  description: |
+    The ``os-update_snapshot_status`` action.
+  in: body
+  required: true
+  type: object
 os-vol-host-attr:host:
   description: |
     Current back-end of the volume.
@@ -2483,6 +2489,12 @@ snapshot_id_4:
   in: body
   required: true
   type: string
+snapshot_progress:
+  description: |
+    A percentage value for snapshot build progress.
+  in: body
+  required: false
+  type: string
 snapshots_number:
   description: |
     The number of snapshots that are allowed for each project.

api-ref/source/v3/samples/snapshot-status-update-request.json

@@ -0,0 +1,6 @@
+{
+    "os-update_snapshot_status": {
+        "status": "creating",
+        "progress": "80%"
+    }
+}

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

@@ -3,7 +3,8 @@
 Snapshot actions (snapshots, action)
 ====================================
 
-Administrator only. Resets status for a snapshot.
+Administrator only, depending on policy settings.
+Resets, updates status for a snapshot.
 
 
 Reset a snapshot's status
@@ -36,3 +37,37 @@ Request Example
 
 .. literalinclude:: ./samples/snapshot-status-reset-request.json
    :language: javascript
+
+
+Update status of a snapshot
+~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+.. rest_method::  POST /v3/{project_id}/snapshots/{snapshot_id}/action
+
+Update fields related to the status of a snapshot.
+Specify the ``os-update_snapshot_status`` action in the request body.
+
+Response codes
+--------------
+
+.. rest_status_code:: success ../status.yaml
+
+   - 202
+
+
+Request
+-------
+
+.. rest_parameters:: parameters.yaml
+
+   - project_id: project_id_path
+   - snapshot_id: snapshot_id_path
+   - os-update_snapshot_status: os-update_snapshot_status
+   - status: status_2
+   - progress: snapshot_progress
+
+Request Example
+---------------
+
+.. literalinclude:: ./samples/snapshot-status-update-request.json
+   :language: javascript