prepare next release (#1536)

Author: jderusse

CHANGELOG.md

@@ -1,13 +1,18 @@
 # Change Log
 
-## NOT RELEASED
+## 1.20.0
 
 ### Added
 
 - Support for LocationService
 - Support for hostPrefix in requests
 - AWS api-change: API updates for the AWS Security Token Service
 - Support for SSO credentials
+- Avoid overriding the exception message with the raw message
+
+### Changed
+
+- Improve parameter type and return type in phpdoc
 
 ## 1.19.0