public interface ExternalContext
ExternalContext can be used to pass components created and managed outside of Samza into a Samza
application. This will be made accessible through the Context.
This is passed to ApplicationRunner.run(ExternalContext) and propagated down to the
Context object provided to tasks.
ExternalContext can be used to inject objects that need to be created by other frameworks, such as Spring.
This is currently just a marker interface for the object passed into Samza.