Add API ref for <ClusterID>/actions/resize

Task: 29737
Story: 2005054

Change-Id: I5511303c8c08a330bdfc0104290c6f8f1831e4b2

api-ref/source/clusters.inc

@@ -263,3 +263,60 @@ Response Example
 
 .. literalinclude:: samples/cluster-create-resp.json
    :language: javascript
+
+
+Resize a cluster
+================
+
+.. rest_method:: POST /v1/clusters/{cluster_ident}/actions/resize
+
+Resize a cluster.
+
+Response Codes
+--------------
+
+.. rest_status_code:: success status.yaml
+
+   - 202
+
+.. rest_status_code:: error status.yaml
+
+   - 401
+   - 403
+   - 404
+   - 409
+
+Request
+-------
+
+.. rest_parameters:: parameters.yaml
+
+  - cluster_ident: cluster_ident
+  - node_count: node_count
+  - nodes_to_remove: nodes_to_remove
+  - nodegroup: nodegroup
+
+.. note::
+
+   The nodegroup is just a placeholder for future. It hasn't been supported
+   in Magnum now.
+
+Request Example
+----------------
+
+.. literalinclude:: samples/cluster-resize-req.json
+   :language: javascript
+
+Response
+--------
+
+.. rest_parameters:: parameters.yaml
+
+  - X-Openstack-Request-Id: request_id
+  - uuid: cluster_id
+
+Response Example
+----------------
+
+.. literalinclude:: samples/cluster-create-resp.json
+   :language: javascript

api-ref/source/parameters.yaml

@@ -428,12 +428,25 @@ node_count:
   in: body
   required: true
   type: integer
+nodegroup:
+  description: |
+    The ID of node group. A node group is a subset of node instances within
+    a cluster that all have the same configuration.
+  in: body
+  required: false
+  type: string
 nodes:
   description: |
     The total number of nodes including master nodes.
   in: body
   required: true
   type: integer
+nodes_to_remove:
+  description: |
+    The server ID list will be removed.
+  in: body
+  required: false
+  type: array
 op:
   description: |
     The operation used to modify resource's attributes. Supported operations

api-ref/source/samples/cluster-resize-req.json

@@ -0,0 +1,5 @@
+{
+    "node_count": 3,
+    "nodes_to_remove": ["e74c40e0-d825-11e2-a28f-0800200c9a66"],
+    "nodegroup":　"production_group"
+}