Add user_id request parameter in os-keypairs list

Added user_id in request parameter section of the
os-keypairs LIST method api-ref docs.

Closes bug: #1599911

Change-Id: Ibb52663b2890f6d46b125903b438c0142aba92f5

api-ref/source/os-keypairs.inc

@@ -17,6 +17,13 @@ Normal response codes: 200
 
 Error response codes: unauthorized(401), forbidden(403)
 
+Request
+-------
+
+.. rest_parameters:: parameters.yaml
+
+  - user_id: keypair_user
+
 Response
 --------
 

api-ref/source/parameters.yaml

@@ -484,6 +484,14 @@ keypair_type_in:
   description: |
     The type of the keypair. Allowed values are ``ssh`` or ``x509``
   min_version: 2.2
+keypair_user:
+  in: query
+  required: false
+  type: string
+  description: |
+    This allows adminstrative users to list key-pairs of specified
+    user ID.
+  min_version: 2.10
 limit:
   description: |
     Requests a page size of items. Returns a number of items up to a limit value.