Deltas must be applied in reverse to reproduce the state of the bucket or
rate data at that point in time, which is then paired with the delta that
will transform it into the previous state.
getDeltas should be encapsulated. It looks like it was public for the sake
of the tests, and its behavior can be inferred by looking at the result of
processing.
Move create config functions out of the main delta-processor.ts file. Change some any types to more specific types. Define document structure better. Move prometheus logic out of processor class. Do not call logger directly, listen for events and log them. Change logger to more PSR-3 compliant style. Extract amqp connection into its own class. Create avro and mongo objects in factory.