Update api-ref for Range request support

This patch updates the api-ref to indicate that ``Range`` shall be
accepted in the request header and upon a successful serving of the
partial image data, the response headers would include ``Content-Range``.

Change-Id: I99ecc345793c7f3045400e57711f01cae2181f6f
Depends-On: b7ebc792c32995751744be3f36cbc9a0c1eead2a

api-ref/source/v2/images-data.inc

@@ -130,8 +130,7 @@ Request
 .. rest_parameters:: images-parameters.yaml
 
    - image_id: image_id-in-path
-   - Content-Range: Content-Range
-
+   - Range: Range
 
 Response
 --------
@@ -140,3 +139,4 @@ Response
    - Content-Type: Content-Type-data-response
    - Content-Md5: Content-Md5
    - Content-Length: Content-Length
+   - Content-Range: Content-Range

api-ref/source/v2/images-parameters.yaml

@@ -56,6 +56,15 @@ Location:
   in: header
   required: true
   type: string
+Range:
+  description: |
+    The range of image data requested. Note that multi range requests are
+    not supported. For details, see
+    `Hypertext Transfer Protocol (HTTP/1.1): Range Requests
+    <http://tools.ietf.org/html/rfc7233>`_.
+  in: header
+  required: false
+  type: string
 
 # variables in path
 image_id-in-path: