Plugin server ingestion base

[Twixes]

Changes

This is some base changes to the Django server, that'll allow us to get started with moving ingestion to the Node plugin server.

All EE events get logged to a new Kafka topic events_handoff, from which the plugin server consumes them (we can't use events_write_ahead_log as consuming messages deletes them, and in the case of a log we want to keep them just in case).
No new topic, as turns out we can reuse the WAL topic. So all EE events will get logged to the existing topic. Removed LOG_TO_WAL setting.

[mariusandra]

Looks good to me! Just in case get buy-in from @fuziontech that nothing else has to be done to emit to a new kafka topic.

[mariusandra]

There's also one failing test

[fuziontech]

(we can't use events_write_ahead_log as consuming messages deletes them, and in the case of a log we want to keep them just in case)

The nice thing about Kafka is that this is not true. Messages are persistent until they TTL out. You should be able to consume from WAL no problem