NotificationPluginApi should not throw PaymentPluginApiException

[pierre]

Any runtime exception in a notification plugin will result in the following stacktrace:

Caused by: java.lang.IllegalStateException: Unexpected PaymentApiException for notification plugin
        at com.ning.billing.osgi.bundles.jruby.JRubyNotificationPlugin.handleKillbillEvent(JRubyNotificationPlugin.java:46)
        at com.ning.killbill.osgi.libs.killbill.OSGIKillbillEventDispatcher$1$1.update(OSGIKillbillEventDispatcher.java:64)
        at java.util.Observable.notifyObservers(Observable.java:159)
        at com.ning.billing.osgi.KillbillEventObservable.handleKillbillEvent(KillbillEventObservable.java:61)
        ... 13 more

It looks like we need to introduce a NotificationPluginApiException. It might be tricky to do the dispatch to the right exception in the generator, maybe we also need a generic PluginApiException that we can convert later on from the Java code.

See:

• https://github.com/killbill/killbill-java-parser/blob/master/src/main/java/com/ning/killbill/generators/ruby/JRubyPluginGenerator.java#L198
• https://github.com/killbill/killbill-plugin-framework-ruby/blob/master/lib/killbill/gen/plugin-api/notification_plugin_api.rb#L53