Add Muthu Subramanian to AUTHORS

AUTHORS.rst

@@ -42,3 +42,6 @@ Ivan Shapovalov <intelfx100 at gmail.com>
 Eric Myhre <hash at exultant.us>
  * Fix bug where ``media_store_path`` config option was ignored by v0 content
    repository API.
+
+Muthu Subramanian <muthu.subramanian.karunanidhi at ericsson.com>
+ * Add SAML2 support for registration and logins.