Adding revoke token write-up.

docs/tutorial/tutorial.rst

@@ -7,3 +7,4 @@ Tutorials
    tutorial_01
    tutorial_02
    tutorial_03
+   tutorial_04

docs/tutorial/tutorial_04.rst

@@ -0,0 +1,45 @@
+Part 4 - Revoking an OAuth2 Token 
+====================================
+
+Scenario
+--------
+You've granted a user an :term:`Access Token`, following :doc:`part 1 <tutorial_01>` and now you would like to revoke that token, probably in response to a client request (to logout).
+
+Revoking a Token
+--------------
+Be sure that you've granted a valid token. If you've hooked in `oauth-toolkit` into your `urls.py` as specified in :doc:`part 1 <tutorial_01>`, you'll have a URL at `/o/revoke_token`. By submitting the appropriate request to that URL, you can revoke a user's :term:`Access Token`.
+
+`Oauthlib <https://github.com/idan/oauthlib>`_ is compliant with https://tools.ietf.org/html/rfc7009, so as specified, the revocation request requires:
+
+- token:  REQUIRED, this is the :term:`Access Token` you want to revoke 
+- token_type_hint: OPTIONAL, designating either 'access_token' or 'refresh_token'.    
+
+Note that these revocation-specific parameters are in addition to the authentication parameters already specified by your particular client type.   
+
+Setup a Request
+----------------
+Depending on the client type you're using, the token revocation request you may submit to the authentication server mayy vary. A `Public` client, for example, will not have access to your `Client Secret`. A revoke request from a public client would omit that secret, and take the form:
+
+::
+
+    POST /o/revoke_token/ HTTP/1.1
+    Content-Type: application/x-www-form-urlencoded
+    token=XXXX&client_id=XXXX
+
+Where token is :term:`Access Token` specified above, and client_id is the `Client id` obtained in 
+obtained in :doc:`part 1 <tutorial_01>`. If your application type is `Confidential` , it requires a `Client secret`, you will have to add it as one of the parameters: 
+
+::
+
+    POST /o/revoke_token/ HTTP/1.1
+    Content-Type: application/x-www-form-urlencoded
+    token=XXXX&client_id=XXXX&client_secret=XXXX
+
+
+The server will respond wih a `200` status code on successful revocation. You can use `curl` to make a revoke request on your server. If you have access to a local installation of your authorization server, you can test revoking a token with a request like that shown below, for a `Confidential` client. 
+
+::
+
+    curl --data "token=XXXX&client_id=XXXX&client_secret=XXXX" http://localhost:8000/o/revoke_token/
+
+