Update change log for release/20.0.0

Author: cslzchen

CHANGELOG.md

@@ -1,3 +1,29 @@
 # Changelog
 
 We follow the CalVer (https://calver.org/) versioning scheme: YY.MINOR.MICRO.
+
+20.0.0 (09-02-2020)
+===================
+
+OSF CAS first release with basic authentication features for OSF
+
+* Username and password login
+* Username and verification key login
+* Two-factor authenticaion
+* Long-term authentication
+* ORCiD login
+
+Technical details
+
+* JSON service registry
+* JPA ticket regisrtry with PostgreSQL
+* JPA PostgreSQL authentication backend
+* Customized login web flow and authentication including:
+  * OSF credential and metadata populator
+  * OSF non-interactive authentication action
+  * OSF PostgreSQL authentication handler
+  * Pac4j authentication delegation
+  * Two-factor authentication using time-based one-time password
+  * Customized authentication exception handling
+  * Customized user interface
+