docs: Add multi-policy validation documentation

This patchset adds multi-policy validation documentation to the
developer's documentation section. Also adds REVIEWING guidelines
to help developers/reviewers understand guidelines/best practices
for writing such tests.

Change-Id: Ieb462e3b176a5dba40146ddd422e62e5715dc034
diff --git a/doc/source/rbac-overview.rst b/doc/source/rbac-overview.rst
index 09ab17d..acfd66f 100644
--- a/doc/source/rbac-overview.rst
+++ b/doc/source/rbac-overview.rst
@@ -124,12 +124,9 @@
   degree of log tracing is required by developers to confirm that the expected
   policies are getting enforced, prior to the tests getting merged.
 
-.. todo::
+For more information, see :ref:`multi-policy-validation`.
 
-  Link to multi-policy validation documentation section once it has been
-  written.
-
-.. _error-codes:
+.. _policy-error-codes:
 
 Error Codes
 -----------
@@ -196,7 +193,7 @@
     in an exception getting raised or a boolean value getting returned.
     Hard authorization results in an exception getting raised. Usually, this
     results in a ``403 Forbidden`` getting returned for unauthorized requests.
-    (See :ref:`error-codes` for further details.)
+    (See :ref:`policy-error-codes` for further details.)
 
     Related term: :term:`soft authorization`.