Common: support new Avro enriched event format

[chuwy]

To maintain compatibility between the Hadoop pipeline (which will continue to use the TSV format for now) and the Kinesis pipeline (which can evolve to using the new Avro format much quicker), we should make this an outbound facade. In other words, Scala Common Enrich should be able to emit both formats.

[chuwy]

Migrated from https://github.com/snowplow/snowplow/issues/1634 (comments are auto-generated)

[devorbit]

Hi @chuwy

Are we still thinking of it?

[benjben]

Hi @devorbit , no this is not on the radar