What would you like to be added:

dnstap supports sending extra bytes in the payload. This is defined in the dnstap.proto
However, the dnstap plugin and forward plugin which uses dnstap do not allow sending this extra field. Hence, this enhancement request to update the dnstap plugin to support sending the extra bytes.

There is no limit to the size of the extra but we can cap it based on a config.

Why is this needed:

We have a use-case where we want to add some extra meta-data/context in the dns log to be sent to the dnstap receiver.