[api-ref] Update volume metadata for a specific key (v2)

This patch is to add api-ref for cinder v2 api: update volume metadata
for a specific key.

Change-Id: I6aa92c3b56ed08830c82f7adbbf8dcb36e980162

api-ref/source/v2/parameters.yaml

@@ -71,6 +71,13 @@ key_2:
   in: path
   required: true
   type: string
+key_3:
+  description: |
+    The metadata key name for the metadata that you
+    want to update.
+  in: path
+  required: true
+  type: string
 project_id_path:
   description: |
     The UUID of the project in a multi-tenancy cloud.
@@ -915,6 +922,12 @@ maxTotalVolumes:
   in: body
   required: true
   type: integer
+meta:
+  description: |
+    The metadata key and value pair for the volume.
+  in: body
+  required: true
+  type: object
 metadata:
   description: |
     One or more metadata key and value pairs for the

api-ref/source/v2/samples/volume-metadata-update-key-request.json

@@ -0,0 +1,5 @@
+{
+  "meta": {
+    "name": "new_name"
+  }
+}

api-ref/source/v2/samples/volume-metadata-update-key-response.json

@@ -0,0 +1,5 @@
+{
+  "meta": {
+    "name": "new_name"
+  }
+}

api-ref/source/v2/volumes-v2-volumes.inc

@@ -648,3 +648,45 @@ Request
    - tenant_id: tenant_id
    - volume_id: volume_id_path
    - key: key_1
+
+
+
+
+Update volume metadata for a specific key
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+.. rest_method::  PUT /v2/{project_id}/volumes/{volume_id}/metadata/{key}
+
+Update metadata for a volume for a specific key.
+
+Normal response codes: 200
+
+
+Request
+-------
+
+.. rest_parameters:: parameters.yaml
+
+   - project_id: project_id_path
+   - volume_id: volume_id_path
+   - key: key_3
+   - meta: meta
+
+Request Example
+---------------
+
+.. literalinclude:: ./samples/volume-metadata-update-key-request.json
+   :language: javascript
+
+Response Parameters
+-------------------
+
+.. rest_parameters:: parameters.yaml
+
+   - meta: meta
+
+Response Example
+----------------
+
+.. literalinclude:: ./samples/volume-metadata-update-key-response.json
+   :language: javascript