Added oauth 2 generation explaination for radicale

doc/installation.rst

@@ -72,6 +72,7 @@ specific part, here are the steps you must follow:
    manual_installation/dovecot
    manual_installation/postfix
    manual_installation/opendkim
+   manual_installation/radicale
 
 Extensions
 ----------

doc/manual_installation/radicale.rst

@@ -0,0 +1,38 @@
+.. _radicale:
+
+#######
+Radicale
+#######
+
+This page is currently being written.
+
+.. _radicale_oauth2:
+
+OAuth 2 authentication
+======================
+
+You first need to register Radicale as an authorized consumer of the
+OAuth2 authentication service provided by Modoboa. To do so, create an
+application with the following commands:
+
+.. sourcecode:: bash
+
+   > cd <modoboa_instance_path>
+   > python manage.py createapplication --name=Radicale --skip-authorization --client-id=radicale confidential client-credentials
+
+On success, you should see an output similar to::
+
+  New application Radicale created successfully.
+  client_secret: XXXX
+
+To enable OAuth2 authentication in Radicale, edit the :file:`/etc/radicale/config`
+file and update the `type` in `[auth]` to::
+
+  type = radicale_modoboa_auth_oauth2
+
+Then, add the following line in `[auth]`::
+
+  oauth2_introspection_endpoint = https://radical:<client_secret>@<hostname of your server>/api/o/introspect/
+
+
+Replace ``<client_secret>`` with the value you obtained earlier.