Use Wire as a replacement for global mutable shared state (e.g. common.BillingId)

[trietsch]

At the moment, we have a global, mutable, shared variable for the BillingId. The initialization process of setting this variable is not transparant.
This is where dependency injection could come to play, which Golang offers (officially built): https://github.com/google/wire

Let's explore if Wire could help us remove the current way common.BillingId works.