This class is the implementation of the event consumer for fulfilling registering an index update request to the processing queue:
- A full re-indexing request is always an asynchronous task executed in a separate transaction at a later time.
- A delta update request can either be both synchronous or asynchronous, depending on the severity of the event. Only events set with SEVERITY_CRITICAL and SEVERITY_FATAL will be executed immediately within the same transaction. Otherwise, events with other severities will be queued as an asynchronous task to be executed in a separate transaction at a later time.