[docs] Added a paragraph on skip_authorization

Added a paragraph to explain the use of the skip_authorization Application attribute.

Author: zopieux

docs/advanced_topics.rst

@@ -62,3 +62,11 @@ Possible values are:
 
 * `auto` - users are prompted only the first time, subsequent authorizations for the same application
   and scopes will be automatically accepted.
+
+Skipping authorization completely for trusted applications
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+You might want to completely bypass the authorization form, for instance if your application is an
+in-house product or if you already trust the application owner by other means. To this end, you have to
+set ``skip_authorization = True`` on the ``Application`` model, either programmaticaly or within the
+Django admin. Users will *not* be prompted for authorization, even on the first use of the application.