The shop name must be used as tag instead of part of the metric.

The CashRegisterAdapter payload is different from the one that is sent from the Django Admin:

• the Django Admin publishes the Receipt object after it has been saved
• the REST API publishes a "converted" serialized object that includes exactly what the cash register library is expecting

We MUST unify the process so that:

• in any situation, the Receipt model is sent to the Adapter instance
• the Django Admin Receipt page is already done and doesn't need more work
• the REST API must send the Receipt instance that has been saved by the serializer
• the conversion logic must be moved from the API to the CashRegisterAdapter.push() method

Unless this work is done, it's not possible to use the CashRegisterAdapter (tests are invalid at the moment).

The goal is to plug external functionalities (like printing a real receipt or pushing data to a third party service)

We must have only one point where Adapters are invoked so that they're used both in the Django Admin and the Receipt API.

It should post values as Datadog metrics to a local or remote Datadog agent, via statsd.