Default DynamoDB table name to stream name instead of logstash

[mkadin]

Thanks for providing this plugin!

Just lost a few hours trying to understand why my pipeline which consumes from two different streams wasn't working correctly. I believe it's because we didn't set the application_name uniquely for the two different input configurations.

Any reason why this shouldn't default to something like logstash-{{stream_name}} instead of just logstash? I'd guess that most users are scoping their tables to the stream name instead of logstash overall.