update readme: add Kc config help

Resources/docs/keycloak-config-guide.md

@@ -0,0 +1,42 @@
+# Keycloak Configuration guide
+
+### Create a realm
+
+We assume that you already have a realm, if not you can create a realm from the Administration UI, go to ```Realm list > Add realm```
+
+![Create a realm](screenshots/create-a-realm.png)
+
+it will appear in the realm list after creation.
+
+### Create a client
+
+You must define a client that will configure the scope of your application security.
+Make sure you already are in your newly created realm and create a new client by going in ```Configure > Clients > Create```.
+
+![Create a client](screenshots/create-a-client.png)
+
+Once created, you can configure it by going in ``` Configure > Clients > [Your client]```
+Here is a sample configuration that work with our bundle :
+
+![Configure client](screenshots/config-client.png)
+> Note that the client Access type is bearer-only.
+
+### Create roles
+ 
+ In keycloak, roles are an abstraction of permissions for our application (used in security.yaml).
+ In our case we need to define a role named **ROLE_API**
+ 
+ You can configure it in ```Configure > Clients > [Your client] > Roles```
+ 
+ ![Create a role](screenshots/create-a-role.png)
+ 
+ ### Assign a role to a user
+
+Last but not least we need to affect our role to our users.
+
+To add role, go to ```Manage > Users > View all users > [Some User] > Role Mappings```.
+
+* In the **Client Roles** dropdown select your client that contains our roles.
+* Select Roles in **Available Roles** list, then click **Add selected** to assign role to the uses.
+
+And your all done, now you can use your client to secure your API.