More info in readme about tests.
A note on Bean Validation
Check payment timestamp.
Move static method to the bottom (finally).
Save any additional properties from the response, and test that there are none (any such json properties should probably be mapped to bean properties).
Save any additional properties from the response, and test that there are none (any such json properties should probably be mapped to bean properties). Add the missing previous_hash, next_hash to Notification.
remove todo