Fix confirmation api doc missing

Zaqar didn't update the api doc after supporting
the confirmation feature.

Change-Id: Iff1e39b4b9d89ff925f5b21774265ea1bc9a0b5f

api-ref/source/parameters.yaml

@@ -329,6 +329,13 @@ claim_ttl:
     the claim. The ttl value must be between 60 and 43200 seconds (12 hours).
     You must include a value for this attribute in your request.
 
+confirmed:
+  type: boolean
+  in: body
+  required: true
+  description: |
+    The ``confirmed`` attribute specifies whether to confirm a subscription.
+
 count:
   type: integer
   in: body

api-ref/source/samples/subscription-confirm-request.json

@@ -0,0 +1,3 @@
+{
+    "confirmed": true
+}

api-ref/source/subscription.inc

@@ -252,3 +252,47 @@ Request Parameters
 
 This operation does not accept a request body and does not return a response
 body.
+
+
+Confirm Subscription
+====================
+
+.. rest_method:: POST /v2/queues/{queue_name}/subscriptions/{subscription_id}/confirm
+
+Confirm a subscription.
+
+This operation can confirm or cancel a subscription.
+
+
+Response codes
+--------------
+
+.. rest_status_code:: success status.yaml
+
+   - 201
+
+.. rest_status_code:: error status.yaml
+
+   - 400
+   - 401
+   - 503
+
+
+Request Parameters
+------------------
+
+.. rest_parameters:: parameters.yaml
+
+  - queue_name: queue_name
+  - subscription_id: subscription_id_path
+  - confirmed: confirmed
+
+
+Request Example
+---------------
+
+.. literalinclude:: samples/subscription-confirm-request.json
+   :language: javascript
+
+
+This operation does not return a response body.