add ldap user federation in sso guide

docs/divers/devops/sso/sso-ldap.md

@@ -94,3 +94,32 @@ Run `docker-compose up -d` to deploy the server.
 
 Access phpmyadmin at `http://127.0.0.1:8092` and connect with user 
 `cn=admin, dn=domain, dn=org` and password set in `env`.
+
+## Create domain under master
+
+You don't want to work in master, instead, you want to keep master as a top-level Realm and create a realm inside 
+for your organisation.
+
+Click on master in the upper-left, then `Add Realm`.
+
+## Set keycloak to federate users from openldap server
+
+### Create new User Federation
+
+Go to your newly created realm (not master), and click on `Configure > User Federation`, then `Add provider`
+
+![screenshot showing user federation creation](img/create-user-federation.png)
+
+### Configure Openldap user federation
+
+#### Basic settings
+
+Use following settings for User federation :  
+
+![screenshot showing basic settings for user federation creation](img/basic-settings-user-federation.png)
+
+#### Add mapper for group
+
+Go to `Mappers` tab, and click on `Create` on the upper-right.
+
+![screenshot showing mapper settings for group mapping](img/group-mapper-settings-user-federation.png)