Stream AuditLogWriter processing cannot be parallelized

Today the audit event listener (StreamAuditEventListener) in charge of writing the log entries to the audit stream is using the log entry id as a key to route the record to a partition.

But the log entry id at this stage is always 0 resulting in routing all the records to a single partition. This prevents using more than a single consumer in the cluster.

This is a problem only when the audit is specifically configured to use more than a single partition (default).

There are cases where we may want to use more than a single partition:

• consumers don't care about the ordering, this is the case for the audit log writer
• support higher throughput on audit log writer
   

Note that using more than one partition is not something that we want by default, this configuration provides a good default:

• preserve a total ordering of log entry events (even with multiple time desynchronized nodes)
• a good constant throughput without using more than 1 thread on the cluster
• prevent stressing the audit backend (elasticsearch) too much

Note that this is specific to 10.10 (LTS 2021 can use more than one partition) it also affects LTS 2021