In order to handle both AWS and Azure limitations on only having one usage event per hour, we need to design a way to aggregate billable_usages for a given hour. 

Questions to address:

• Where should the aggregation occur?

• • tally-worker?
• What timestamps are being sent to the marketplaces?
• Can we use in-memory aggregation without extra topics

AC: 

• design details added to:
  https://docs.google.com/document/d/182b9te5quFusI0ek4SGAJIjKOL1bZkrcT13anOfQNK4/edit
• A miro board detailing the process from tally to marketplace.

A PoC has been completed for using kstreams here:
https://github.com/RedHatInsights/rhsm-subscriptions/pull/3012