When enriching the events the call to the MW API might fail in different ways. Even if we attempt retries there might be situations in which we have to abandon the process to avoid stalling the whole pipeline. In these cases we might have to record such problems in a "side-output". This side-output will produce events to a kafka topic and thus we have to design a schema for describing such events.
AC:
- the schema defines all the required information to understand the cause of the failure and to eventually "reconcile" this item at a later time
- a schema is added to schema.wikimedia.org