Research and implement cost allocation

[riccardomc]

A crucial point of this effort is allocating costs of the underlying infrastructure to paying customers. In order to do that, we need to track resource usage by said customers and bill them accordingly. Again, this will be a critical part of this project.

@piyush82 has experience in this area and his input will be precious.

Part of this effort is related to the ability of enforcing limits in #1 and #2.

While this is not directly relevant for both the Free Tier and the PoC, we need to have something in place in order to leverage the data we get by user activity and validate our cost allocation mechanisms.