Allow sending arbitrary messsages using [`pg_logical_emit_message`](https://www.postgresql.org/docs/9.6/static/functions-admin.html) adding the [proper callback](https://www.postgresql.org/docs/9.6/static/logicaldecoding-output-plugin.html#LOGICALDECODING-OUTPUT-PLUGIN-MESSAGE). See https://github.com/eulerto/wal2json/pull/20 for a similar implementation.
Allow sending arbitrary messsages using
pg_logical_emit_messageadding the proper callback.See eulerto/wal2json#20 for a similar implementation.