docs: add references to Flask-Appbuilder Security documentation (#3322)

And a specific link to an oauth example configuration.

docs/faq.rst

@@ -173,7 +173,7 @@ different sections of the code do:
 https://github.com/airbnb/superset/pull/3013
 
 What database engine can I use as a backend for Superset?
---------------------------------------------------------
+---------------------------------------------------------
 
 To clarify, the *database backend* is an OLTP database used by Superset to store its internal
 information like your list of users, slices and dashboard definitions.
@@ -184,3 +184,9 @@ install Superset on one of these database server for production.
 Using a column-store, non-OLTP databases like Vertica, Redshift or Presto as a database backend simply won't work as these databases are not designed for this type of workload. Installation on Oracle, Microsoft SQL Server, or other OLTP databases may work but isn't tested.
 
 Please note that pretty much any databases that have a SqlAlchemy integration should work perfectly fine as a datasource for Superset, just not as the OLTP backend.
+
+How can i configure OAuth authentication and authorization?
+-----------------------------------------------------------
+
+You can take a look at this Flask-AppBuilder `configuration example 
+<https://github.com/dpgaspar/Flask-AppBuilder/blob/master/examples/oauth/config.py>`_.

docs/security.rst

@@ -3,7 +3,8 @@ Security
 Security in Superset is handled by Flask AppBuilder (FAB). FAB is a
 "Simple and rapid application development framework, built on top of Flask.".
 FAB provides authentication, user management, permissions and roles.
-
+Please read its `Security documentation 
+<http://flask-appbuilder.readthedocs.io/en/latest/security.html>`_.
 
 Provided Roles
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