Can we add the port attribute to connection. This might be useful before the full document API is implemented. Some datasource changes could need to change the port in addition to the server etc. Some changes are a bit more involved but could include a port change. For example migrating from AWS RDS Postgres to Redshift might mean changing port from 5432 to 5439. A change of database variant could require other changes of course - schema in the relation for example.