ONOS-2486 Adding swagger-based REST API documentation.

Change-Id: I237d973d73549ad30ddc638c1c201f024d344c70
diff --git a/web/api/src/main/java/org/onosproject/rest/resources/ClusterWebResource.java b/web/api/src/main/java/org/onosproject/rest/resources/ClusterWebResource.java
index 690637e..ee608b7 100644
--- a/web/api/src/main/java/org/onosproject/rest/resources/ClusterWebResource.java
+++ b/web/api/src/main/java/org/onosproject/rest/resources/ClusterWebResource.java
@@ -37,19 +37,32 @@
 import static org.onlab.util.Tools.nullIsNotFound;
 
 /**
- * REST resource for interacting with the ONOS cluster subsystem.
+ * Manage cluster of ONOS instances.
  */
 @Path("cluster")
 public class ClusterWebResource extends AbstractWebResource {
 
     public static final String NODE_NOT_FOUND = "Node is not found";
 
+    /**
+     * Get all cluster nodes.
+     * Returns array of all cluster nodes.
+     *
+     * @return 200 OK
+     */
     @GET
     public Response getClusterNodes() {
         Iterable<ControllerNode> nodes = get(ClusterService.class).getNodes();
         return ok(encodeArray(ControllerNode.class, "nodes", nodes)).build();
     }
 
+    /**
+     * Get cluster node details.
+     * Returns details of the specified cluster node.
+     *
+     * @param id cluster node identifier
+     * @return 200 OK
+     */
     @GET
     @Path("{id}")
     public Response getClusterNode(@PathParam("id") String id) {
@@ -58,6 +71,13 @@
         return ok(codec(ControllerNode.class).encode(node, this)).build();
     }
 
+    /**
+     * Forms cluster of ONOS instances.
+     * Forms ONOS cluster using the uploaded JSON definition.
+     *
+     * @param config cluster definition
+     * @return 200 OK
+     */
     @POST
     @Path("configuration")
     public Response formCluster(InputStream config) throws IOException {