[install] Add the multiple domain configuration

backport:Liberty

Change-Id: Ie019c1ca6140d0bfaba84129403da733de180cc0
Closes-Bug: #1416954

doc/install-guide/source/horizon-install.rst

@@ -125,6 +125,22 @@ Install and configure components
 
            OPENSTACK_KEYSTONE_DEFAULT_ROLE = "user"
 
+      * Enable the multi-domain model:
+
+        .. code-block:: ini
+
+           OPENSTACK_KEYSTONE_MULTIDOMAIN_SUPPORT = True
+
+      * Configure the service API version so that you can log into
+        the dashboard by the Keystone V3 API:
+
+        .. code-block:: ini
+
+           OPENSTACK_API_VERSIONS = {
+               "identity": 3,
+               "volume": 2,
+           }
+
       * If you chose networking option 1, disable support for layer-3
         networking services:
 
@@ -193,6 +209,22 @@ Install and configure components
 
            OPENSTACK_KEYSTONE_DEFAULT_ROLE = "user"
 
+      * Enable the multi-domain model:
+
+        .. code-block:: ini
+
+           OPENSTACK_KEYSTONE_MULTIDOMAIN_SUPPORT = True
+
+      * Configure the service API version so that you can log into
+        the dashboard by the Keystone V3 API:
+
+        .. code-block:: ini
+
+           OPENSTACK_API_VERSIONS = {
+               "identity": 3,
+               "volume": 2,
+           }
+
       * If you chose networking option 1, disable support for layer-3
         networking services:
 
@@ -261,6 +293,22 @@ Install and configure components
 
            OPENSTACK_KEYSTONE_DEFAULT_ROLE = "user"
 
+      * Enable the multi-domain model:
+
+        .. code-block:: ini
+
+           OPENSTACK_KEYSTONE_MULTIDOMAIN_SUPPORT = True
+
+      * Configure the service API version so that you can log into
+        the dashboard by the Keystone V3 API:
+
+        .. code-block:: ini
+
+           OPENSTACK_API_VERSIONS = {
+               "identity": 3,
+               "volume": 2,
+           }
+
       * If you chose networking option 1, disable support for layer-3
         networking services:
 

doc/install-guide/source/horizon-verify.rst

@@ -18,4 +18,5 @@ Verify operation of the dashboard.
    Access the dashboard using a web browser at
    ``http://controller/horizon``.
 
-Authenticate using ``admin`` or ``demo`` user credentials.
+Authenticate using ``admin`` or ``demo`` user
+and ``default`` domain credentials.