[placement] Add api-ref for GET RP inventory

This provides simple documentation of the response body and path
parameters when showing a single class of inventory for a resource
provider.

Change-Id: Ic562baa3e74445c8f6dbeb416c1ec183cc2ad14d

placement-api-ref/source/get-inventory.json

@@ -0,0 +1,9 @@
+{
+    "allocation_ratio": 16.0,
+    "max_unit": 4,
+    "min_unit": 1,
+    "reserved": 0,
+    "resource_provider_generation": 9,
+    "step_size": 1,
+    "total": 4
+}

placement-api-ref/source/index.rst

@@ -15,3 +15,4 @@ Openstack Placement API concepts, please refer to the
 .. include:: root.inc
 .. include:: resource_providers.inc
 .. include:: inventories.inc
+.. include:: inventory.inc

placement-api-ref/source/inventory.inc

@@ -0,0 +1,44 @@
+===========================
+Resource provider inventory
+===========================
+
+See `Resource provider inventories`_ for a description.
+
+This group of API calls works with a single inventory identified by ``resource_class``.
+One inventory can be listed, created, updated and deleted per each call.
+
+Show resource provider inventory
+================================
+
+.. rest_method:: GET /resource_providers/{uuid}/inventories/{resource_class}
+
+Normal Response Codes: 200
+
+Error response codes: itemNotFound(404)
+
+Request
+-------
+
+.. rest_parameters:: parameters.yaml
+
+  - uuid: resource_provider_uuid_path
+  - resource_class: resource_class_path
+
+Response
+--------
+
+.. rest_parameters:: parameters.yaml
+
+  - resource_provider_generation: resource_provider_generation
+  - allocation_ratio: allocation_ratio
+  - max_unit: max_unit
+  - min_unit: min_unit
+  - reserved: reserved
+  - step_size: step_size
+  - total: total
+
+Response Example
+----------------
+
+.. literalinclude:: get-inventory.json
+   :language: javascript

placement-api-ref/source/parameters.yaml

@@ -1,4 +1,10 @@
 # variables in path
+resource_class_path: &resource_class_path
+  type: string
+  in: path
+  required: true
+  description: >
+    The name of one resource class.
 resource_provider_uuid_path: &resource_provider_uuid_path
   type: string
   in: path
@@ -88,11 +94,8 @@ reserved_opt:
   <<: *reserved
   required: false
 resource_class:
-  type: string
+  <<: *resource_class_path
   in: body
-  required: true
-  description: >
-    The name of the resource class.
 resource_provider_generation:
   type: integer
   in: body