Sources that mirror external database tables

[purplefox]

We can consider sources which get their data from an external database table (e.g. in MySQL or in TiDB) instead of from a Kafka topic.

A CDC tool such as Debezium could be used to get changes from the table and those changes could be pushed directly (or through a Kafka topic) to Prana.

This would be a super powerful feature and would allow Prana to create updating materialized views based on external database tables or combinations of external database tables and Kafka topics!